••• 


ENGIN. 
LIBRARY 


UC-NRLF 


STANDARD 
INSTRUM 

nr 
Ui 


NTS 


C. L.  BERGER  &.  SONS 

Sf  WM.MAM*  STMKCT. 

Boston^Mass,  U.S.A. 


*Kl*lfl?V* 

All  persons  infringing  on  the  Patent  Rights  of  our  instruments  or  Copyright  of  this  Ca^Bgufr^     ^ 
and  Price  List  will  be  prosecuted  to  the  extent  of  the  law.  ***/ 


Engineering 


Prices  —  This  Catalogue  and  Price  List  supersedes  all  former  editions. 
We  make  no  deduction  from  Catalogue  Prices. 

Payments  —  Customers  ordering  from  a  distance  will  please  remit  by 
registered  letter,  express  or  P.  O.  money  order,  or  draft,  made  payable  to 
us,  or  tne  goods  win  be  sent  C.  O.D.,the  expense  of  collection  to  be  borne 
by  the  purchaser.  Accounts  can  only  be  opened  with  firms  rated  by  com- 
mercial agencies  or  upon  receipt  of  other  satisfactory  reference. 

Ordering  —  When  goods  are  ordered  by  telegraph  our  code  should  be  used 
exclusively  (see  back  pages  of  catalogue),  and  then  patrons  (excepting 
states  municipalities,  corporations,  etc.)  who  are  not  known  to  us  should 
also  wire  simultaneously  whether  goods  are  to  be  sent  C.O.D.  or  whether 
payment  is  secured  by  bank  draft  on  Boston  or  New  York.  (SEE  "PAY- 
MENTS," PAGE  M  OF  CODE.)  The  order  shojuld  then  be  confirmed  by  let- 
ter. 

Address  —  Please  be  careful  to  add  the  COUNTY  and  STATE  to  your  ad- 
dress. 

Mail  Orders  —  Small  articles  can  be  sent  by  mail,  at  the  purchaser's  risk, 
when  the  cost  of  postage,  one  cent  for  every  ounce,  is  remitted  in  addition 
to  the  price. 

Shipping  —  Our  instruments  are  carefully  packed  in  their  boxes,  which 
again  are  placed  in  packing  boxes,  as  explained  under  "Transportation  of 
Instruments"  page  18.  This  insures  safest  delivery;  and  being  in  con- 
formity with  the  rules  of  most  of  the  large  Express  Companies,  also  en- 
ables us  to  express  Surveying  Instruments  as  merchandise,  thus  secur- 
ing to  our  customers  single  rates. 

Cable  Address,  BERGER,  Boston. 


PREFACE. 


THE  instruments  enumerated  in  this  catalog,  and  described  in  the  Manual,  are  all 
of  our  own  design  and  regular  manufacture.     Full  supplies  of  Engineers'  and 
Surveyors'  Instruments  will  be  kept  on  hand.     The  demand  is  at  times  so  great, 
however,  as  to  exhaust  our  supply.     To  secure  an  instrument  in  season,  it  is  best  to 
order  it  from  four  to  eight  weeks  in  advance  of  its  intended  use.     Instruments  varying 
from  our  customary  designs,  or  those  of  rare  inquiry,  will  be  made  to  order  only. 

The  mechanical  features  of  our  instruments  are  of  the  most  simple 
and  mechanically  perfect  design  and  the  best  that  modern  machinery  and  methods 
pursued  in  a  most  modern  plant,  equipped  and  operated  wholly  for  this  purpose,  can 
produce. 

The  graduations  of  circles  and  verniers,  being  sharp,  clean  cut  and 
easily  read,  are  of  rare  excellence  and  in  point  of  accuracy  have  no  superior. 

The  optical  qualities  of  our  telescopes  are  in  keeping  with  the  fine- 
ness of  every  other  part  of  the  instruments  in  higher  power  permissible  with  greatest 
illumination  and  sharpest  definition. 

The  spirit  levels  ground  and  used  by  us  are  selected  in  degree  of  sensitiveness 
so  as  to  be  strictly  related  to  the  whole  character  of  the  instruments. 

A  careful  perusal  of  our  catalog-  will  convince  that  in  the  number  of 
styles,  sizes,  new  designs,  and  in  the  adaptation  of  the  various  instruments  to  the  work 
for  which  they  are  intended,  we  offer  instruments  that  only  long  training  and  a  studi- 
ous care  of  the  needs  of  the  engineering  and  surveying  profession  in  all  lines  of  practi- 
cal application  in  the  field,  can  produce. 

Styles  and  sizes  of  the  many  kinds  of  instruments  enumerated  in  this  catalog 
cannot  be  varied  from,  since  all  the  standard  patterns  from  which  the  different  parts 
are  cast  are  made  of  brass  to  insure  best  and  uniform  results.  Any  change  from  them 
often  would  entail  only  extra  expense,  and  lead  to  the  sacrifice  of  other  and  equally 
important  advantages,  without  securing  to  the  customer  any  material  benefit. 

The  combinations  possible  with  each  particular  type  of  instrument  are  printed  on 
the  page  opposite  its  cut,  and  as  a  rule  are  so  complete  as  to  meet  special  and  general 
requirements. 

We  make  no  pretence  at  manufacturing  cheap  instruments  —  our  prices  are 
as  low  as  consistent  with  thoroughness  of  workmanship  and  the  use  of  the  best  mate- 
rials. The  aim  of  the  firm  in  the  future  will  be,  as  it  has  been  since  originally  organ- 
ized by  the  senior  member  in  1871,  to  create  an  American  industry  in  the  art  of  mak- 
ing field  instruments  unsurpassed  either  here  or  abroad,  bringing  to  the  task  the 
judgment  and  experience  of  maturity. 

Our  full  telegraphic  Code,  at  back  of  this  catalog,  will  enable  to  order 
from  a  distance  at  small  expense,  and  our  patrons  may  rely  upon  being  served  as  con- 
scientiously as  if  calling  upon  us  in  person. 


take  this  opportunity  to  thank  our  patrons  for  their  confidence  in  the 
past,  and  assure  them  that  their  future  orders  will  be  executed  with  the  same  care  and 
fidelity  as  heretofore. 

C.  L.  BERGER  &  SONS. 

80029O 


TRAKSTSZ3/LEVELS 


CHARACTERISTIC  FEATURES 
OF  OUR  INSTRUMENTS 

1.  Simplicity  in  Manipulation. 

2.  Lightness,  combined  with  strength* 

3.  Accuracy  of  division. 

4.  Achromatic  telescope,  with  high  power. 

5.  Steadiness  of  adjustments  under  varying  tempera- 

tures. 

6.  Stiffness;   to  avoid  any   tremor  even  in  a  strong 

wind. 

7.  Fine  workmanship  throughout. 

8.  Adapted  to  tropical  and  arctic  conditions. 

9.  Prices  —  EQUITABLE  ! 


DESCRIPTION 

OP  THE 

Essential  Features  of  Our  Instruments. 


Graduation. 

This  very  important  part  of  a  good  instrument  we  guarantee  exact  and  accurately 
centered,  opposite  verniers  reading  the  same.  The  lines  are  straight,  thoroughly 
black  and  uniform  in  width.  There  are  two  double  verniers  in  every  transit  to  read 
angles  with  great  rapidity  as  well  as  to  make  four  separate  readings  at  every  sight, 
when  extreme  accuracy  in  the  repetition  of  angles  is  required.  The  horizontal 
circle  is  graduated  from  0°  to  360°  with  two  sets  of  tigures,  running  in  opposite 
directions  ( unless  ordered  differently,)  and  the  verniers  are  marked  A  and  B .  The 
figures  are  large  and  distinct,  and  to  avoid  mistakes  in  reading,  the  figures  of  these 
two  sets  of  graduations,  and  those  on  the  verniers,  are  inclined  in  opposite  directions, 
thus  indicating  the  directions  in  which  the  verniers  should  be  read. 

Instruments  intended  for  mining  and  mountain  use  can  have  the  verniers  so 
placed  that  they  may  be  read  without  changing  the  position  of  the  engineer  after 
sighting  through  the  telescope. 

Glass  covers  protect  the  arc  and  verniers  from  exposure.  For  ease  in  reading 
the  verniers,  we  have  added  to  most  of  our  instruments  two  plates  of  ground  glass, 
which  cast  a  very  clear  light  on  the  verniers,  in  any  position.  We  recommend  this 
addition  to  all  of  our  more  complete  transits. 

The  graduations  on  our  transits  are  either  on  brass  and  silvered,  or  else  gradu- 
ated on  solid  silver.  The  former  we  can  only  recommend  for  the  more  ordinary 
instruments,  since  imperfections  in  the  brass  or  composition  castings  frequently 
impair  the  graduations,  and  the  silvering  is  apt  to  tarnish  with  time  and  exposure. 

To  graduate  on  solid  silver  adds  $10  to  the  first  outlay  for  the  instrument,  but  its 
many  advantages,  great  permanency  and  smoothness  of  surface  render  it  the  only 
satisfactory  surface  for  fine  graduations. 


The  Telescope. 

All  of  its  lenses  are  ground  especially  for  us,  by  the  best  opticians.  The  teles- 
cope is  perfectly  achromatic,  and  designed  to  furnish  a  large,  flat  field  of  view  with 
high  power  and  yet  without  loss  of  light.  For  this  purpose  the  curves  of  all  our 
lenses  are  ground  by  special  formulae.  The  telescopes  show  objects  right  side 
up,  unless  ordered  otherwise. « 

The  object-glass  has  a  very  large  aperture,  and  is  focussed  by  rack  and  pinion,f 
but  the  eye-piece  is  focussed  by  simply  turning  its  head  to  the  right  or  left  in  an 
improved  screw-like  manner. 

By  a  method  of  construction  peculiar  to  ourselves,  we  are  enabled  to  guarantee 
the  line  of  collimation  correct  for  all  distances  without  making  use  of  the  very  objec- 
tionable adjustment  for  the  object-slide  by  means  of  inner  rings,  which  time  and 
experience  has  proven  to  wear  loose  too  readily,  thus  rendering  this  adjustment 
worse  than  none  at  all. 

The  eye-pieces  are  thoroughly  achromatic,  and  their  lenses  are  mounted  in  such 
a  perfect  manner  (a  method  also  peculiar  to  us)  as  to  require  no  further  adjustment 
with  regard  to  the  axis  of  telescope. 

*It  should  be  remembered  that  the  focal  length  of  the  object  glass  is  limited  in  engineering  instruments  and 
that  a  high  power  is  obtained  only  at  the  sacrifice  of  light.  To  obtain  the  fullest  satisfaction,  telescopes  intend- 
ed for  close  work,  as  in  stadia  measurement,  etc.,  should  invariably  be  ordered  to  be  inverting.  Th« 
brilliancy  with  which  objects  appear  in  such  a  telescope,  owing  to  the  amount  of  light  gained  by 
saving  two  lenses  in  the  eve-piece  is  vary  marked  as  compared  with  one  of  the  same  power  and  focal  length 
showing  objects  erect. 

tThis  rack  and  pinion  motion  is  now  so  placed  upon  our  telescopes  that  it  is  more  easy  of  access  by  either 
hand  than  when  placed  at  the  side,  as  shown  in  most  of  our  cuts. 


The  telescope  of  the  transit  reverses  at  both  the  eye  and  object  ends,  and  is 
thoroughly  balanced  when  focussed  for  a  mean  distance. 

The  telescope  of  the  wye  and  dumpy  level  is  also  balanced  each  way  from  the 
center  of  the  vertical  axis  when  focussed  for  mean  distance  and  with  the  sun-shade 
attached  to  it. 

Spirit-Le  vels . 

The  Spirit  Levels  used  in  our  instruments  are  carefully  ground,  filled  and  tested 
by  us  in  person. 

Those  for  the  highest  class  of  engineering  work  are  sometimes  provided  with  an 
air  chamber  by  which  the  length  of  the  bubble  can  be  regulated  according  to  tem- 
perature. The  levels  for  astronomical  instruments  have  air  chambers,  and  are  tilled 
with  ether,  but  in  field  instruments  ether  is  not  admissable,  owing  to  the  high 
degree  of  expansion  and  contraction  in  that  fluid  with  changes  of  temperature. 
For  these  we  use  a  composition  fluid  that  we  have  found  to  be  more  sensitive  and 
quick-acting  than  that  used  in  instruments  we  have  seen  of  other  makers. 

Our  astronomical  levels  are  so  ground  that  a  depression  through  one  second  of 
arc  causes  a  displacement  of  the  bubble  through  about  ^  of  an  inch.  The  curva- 
ture or  sensitiveness  of  our  levels  for  field  instruments  we  adapt  carefully  to  the 
instruments  and  the  kind  of  work  to  which  they  are  to  be  applied.  With  too  sen- 
sitive a  level  the  position  of  the  bubble  would  be  too  uneasy  to  work  with,  while 
too  low  a  sensitiveness  would  not  reveal  the  firll  qualities  of  an  instrument.  Persons 
ordering  instruments  of  us  will  confer  a  favor  by  stating  for  what  purpose  they  are 
intended,  whether  for  water  works,  for  railroads,  or  for  general  use,  so  that  we 
can  use  our  judgment  for  their  benefit. 

Gradienter  Screw. 

[Seepage  45] 

This  is  attached  to  the  clamp  of  telescope  of  all  of  our  transits  except  the  plain 
transit.  This  attachment  was  first  introduced  ty  Prof.  Stampfer,  of  the  Vienna 
Polytechnic  School.  It  does  not  add  to  the  weight  of  the  instrument,  and  once 
used  we  have  found  it  to  be  universally  approved  by  our  customers.  By  means  of 
it  grades  can  be  established,  and  horizontal  distances,  vertical  angles  and  differences 
of  level  can  be  measured  with  great  rapidity.  Indeed  this  attachment  to  an  en- 
gineer's transit  is  one  of  the  most  useful  introductions  in  practical  engineering. 
It  is  so  universal  in  its  application  to  railroad  and  general  work,  that  when  once 
used  it  will  afterwards  form  an  indispensible  part  of  an  engineer's  outfit. 


Fixed  Stadia  Wires  for  Distance  Measurements. 

We  have  specially  devised  an  optical  and  mechanical  apparatus  for  the  purpose 
of  placing  fixed,  or  non-adjustable  stadia  wires  so  accurately  upon  the  diaphragms 
of  our  telescopes  that  their  distance  apart  will  read  1' :  100"  f  on  any  leveling  rod, 
as  with  the  gradienter  screw,  thus  dispensing  with  a  special  rod. 

It  is  well  known  that  adjustable  stadia  wires  are  so  apt  to  change  their  distance 
apart  with  every  change  of  temperature,  that  no  reliance  can  be  placed  upon  them 
unless  previously  adjusted.  With  fixed  stadia  wires,  annoyances  of  this  kind  are 
obviated — they  are  reliable  at  all  times. 

As  regards  the  degree  of  accuracy  attainable  by  the  use  of  fixed  stadia  wires, 
experiments  with  our  powerful  telescopes,  made  optically  as  perfect  as  the  most 
advanced  optical  and  mechanical  skill  enables  us,  warrant  to  say  that  with  some 
experience  and  proper  care  the  results  obtained  will  approximate  and  even  equal 
those  obtained  by  chain  measurements.  The  price  for  this  accessory  in  any  new 
instrument  is  only  $3.00,  but  if  inserted  into  a  telescope  sent  to  us  for  that  purpose, 
we  must  charge  $10.00.  We  advise  to  order  both  the  gradienter  screw  and  the 
fixed  stadia  wires,  as  each  in  itself,  separately  or  jointly,  will  prove  of  great  value. 

t  In  all  stadia  work,  the  instrument  constant,  which  is  the  distance  from  the  center  of  the  instru- 
ment to  a  point  in  front  of  the  object-glass  equal  to  its  focal  length,  must  be  added  to  every  measurement, 
whether  100  or  1000  feet,  and  does  not  vary. 

Instrument  Constant  for 


Transit  Nos.  1,  5  and  11  erect  telescope  1.15  ft. 

"  "        "     "      "  invert.       "          i-37  " 

Transit  Nos.  2,  3  and  6   erect  .04  " 

Transit  No.  4  erect         "  .74 


Transit  No.  4  invert,  telescope  .88  ft 

Wye  Level,  18-inch          erect         "         1.90 " 
invert.  2.14" 

Wye  Level,  14-inch          erect         "         1.41" 


Dumpy  Level,  17%  inch  erect         "         1.65" 
Dumpy  Level,  15-inch  invert  telescope   1.12  ft. 
To  find  the  Wire  Constant.     First  lay  off  from  the  center  of  the  instrument,  the  instrument  con- 
stant, which  is  the  distance  from  a  point  in  front  of  the  object-glass,  equal  toils  focal  length  measured  from 
the  center  of  the  instrument.     Then  measure  off  100  feet  and  place  the  rod  truly  vertical  at  this  distance. 

Determine  the  space  on  the  level  rod  intercepted  by  the  stadia  wires.  The  difference  between  this  read- 
ing and  one  foot  will  be  the  wire  constant,  which  may  be  plus  or  minus,  and  this  constant  must  be  applied  t» 
every  100  feet  measured,  the  amount  varying  with  the  distance  measured. 


Tangent  Screws. 

These  are  made  of  Aluminum  bronze,  or  phosphor  bronze,  and  sometimes  of  ger- 
man  silver,  and  are  provided  with  strong  spiral  springs  of  german  silver,  which  take  up 
all  the  dead  motion,  no  matter  how  long  the  screw  may  be  in  use,  or  how  worn. 
They  are  less  liable  to  get  out  of  order,  by  blows  or  accidents,  than  any  of  the  ex- 
isting tangent  screws,  and  require  little  or  no  attention  on  the  part  of  the  engineer. 
There  is  no  strain  on  either  plate  when  the  instrument  is  clamped,  so  that  the  levels 
are  unaffected.  They  are  set  and  turned  with  the  greatest  ease,  following  the  move- 
ments of  the  finger  instantaneously  with  mathematical  precision,  and  do  not  scratch 
the  plate  in  revolving  instrument.  We  confidently  recommend  this  form  of  con- 
struction to  those  who  have  not  used  our  instruments,  as  the  best  possible;  super- 
seding the  usual  methods  by  means  of  two  opposing  screws,  or  ball  tangent  screw, 
greatly  in  point  of  convenience  and  accuracy,  and  equaling  them  in  point  of  steadi- 
ness. By  this  construction  we  are  also  able  to  fit  our  upper  and  lower  circle  plates 
so  snugly  that  it  is  impossible  for  dust  to  enter  between  them.  Our  leveling  instru- 
ments have  the  clamp  and  tangent  screws  so  placed  that  they  can  be  reached  by 
either  hand  with  the  same  readiness. 


The  Compass. 

The  Compass  circles  are  graduated  to  half  degrees  in  quadrants  from  0°  to  90°. 

The  needles  are  made  of  superior  steel,  and  tempered  all  over.    A  coil  of  fine  wire 

attached  to  the  end  pointing  South  balances  the  needle  for  our  latitude,  which  must 

be  re-balanced  if  the  instrument  is  used  further  north  or  south  of  this  latitude,  and 

must  be  entirely  reversed  if  used  on  the  southern  hemisphere  of  our  earth.    At  a 

cost  of  $  10.00  a  variation  plate  can  be  placed  upon  our  surveyors'  transit  to  set  oft 

the  variation  of  the  needle  for  any  particular  locality.    A  stationary  pointer  just 

above  the  graduated  ring  at  the  North  end,  and  protected  by  the  glass  cover  of  the 

compass,  indicates  the  line  joining  the  vertical  plane  of  the  line  of  collimation  of  the 

telescope.     By  means  of  a  milled-headed  screw  and  clamping  nut,  serving  both  as  a 

handle  and  a  clamp-screw,  the  graduated  ring  can  be  turned  past  this  pointer  towards 

East  or  West  as  the  case  may  require. 

If  it  is  desired  to  set  off  the  variation  more  closely  than  half  degrees,  say  to  minutes, 
this  can  be  done  on  the  horizontal  plate.  For  more  information  concerning  the  oper- 
ation of  the  variation  plate,  read  latter  part  of  the  article  on  the  compass,  page  44. 


Tripod. 

The  form  we  adopt  for  our  instruments  is  an  improvement  over  what  is  com- 
monly termed  the  "  split  leg  "  tripod,  used  extensively  in  Europe,  which  unites  the 
greatest  strength  and  steadiness  with  the  least  weight.  The  tripod-head  is  cast  in  a 
single  casting,  to  avoid  all  small  screws,  as  well  as  to  attain  greater  stiffness.  For 
the  legs  we  use  the  best  fine  grained  white  ash,  taking  particular  pains  that  the 
grain  of  the  wood  runs  in.  the  direction  of  the  leg.  They  are  still  further  guarded 
against  all  possible  accidents  by  wooden  tongues  inserted  at  their  top.  When 
folded,  our  tripod  is  better  adapted  than  the  ordinary  form,  for  carrying  on  the 
shoulder  without  irritating  the  place  on  which  it  rests.  The  good  qualities  of  this 
over  the  ordinary  round  leg  tripod  provided  as  that  is  with  unyielding  brass  cheeks 
to  "tighten"  the  legs,  are  so  great  that  there  is  but  one  opinion  regarding  its  real 
advantages,  and  we  gladly  bear  the  greater  expense  incurred  in  its  manufacture.  The 
cast-steel  shoes  have  projections  for  the  foot,  to  aid  in  pressing  the  legs  into  the 
ground.  Our  levels  and  transits  both  fit  the  same  tripod,  and  are  of  equal  length. 


Shifting:  Tripod. 

We  have  also  adapted  to  all  our  engineers'  transits  the  shifting  tripod  or  shifting 
center,  by  which,  after  an  approximate  setting  of  the  tripod,  the  transit  can  be 
immediately  brought  over  a  point  on  the  ground.  This  device  we  also  attach  to 
our  instruments  with  three  leveling  screws  in  a  roost  perfect  and  simple  manner, 
and  without  impairing  their  steadiness  and  portability. 

Adjustable  Plumb-Bob. 

We  furnish  with  all  our  transits  a  small  brass  chain  and  hook,  which  are 
connected  to  the  centers  of  the  instruments.  The  cord  of  the  plumb-bob  can  be 
readily  attached  or  detached  from  this  hook,  and  by  means  of  a  neat,  small  and 
simple  device,  (also  furnished  with  every  instrument,)  the  plumb-bob  can  be  ad- 
justed over  the  ground  at  any  height,  with  hardly  any  effort  on  the  part  of  the 
engineer. 


Illumination  of  Cross-Wires 

For  Mining  and  Tunnel  Transits. 

In  our  instruments  this  sometimes  consists  of  a  hole  drilled  through  the  transverse  axis 
of  the  telescope,  and  closed  at  either  end  with  small  glass  plates,  to  prevent  dust  entering 
the  telescope  Then  in  the  center  of  the  telescope  is  placed  a  small  adjustable  reflector, 
by  means  of  which  the  cross-wires  can  be  very  readily  illuminated  m  the  mine  or  tunnel  by 
the  reflection  of  the  light  of  a  lamp  held  in  the  hand  or  placed  on  a  small  table,  which  is 
attached  to  the  standard.  This  lamp  is  provided  with  a  ground  lens.  \\  bile  this  method 
is  satisfactory,  still  the  small  mirror  has  to  be  placed  at  a  point  where  the  cone  of  rays 
from  the  object  glass  is  small  and  consequently  it  cuts  off  much  of  the  best  part  of  the 
litrht  not  to  speak  of  the  weight  of  the  lamp  and  table  at  the  side  of  the  standard  and  the 
heat  'imparted.  This  method  is  not  thought  to  be  of  as  good  repute  as  it  was  formerly. 
In  all  cases  we  would  advise  the  use  of  our  reflector,  placed  in  front  of  the  object  glass  in 
a  tube  like  the  sun-shade.  This  arrangement  gives  perfect  satisfaction.  This  may  be  used 
in  connection  with  an  ordinary  lamp  or  with  the  pocket  electric  lamp. 

Arrangement  for  Offsetting  at  Right  Angles. 

A  perfect  line  of  sight  can  be  had  at  right  angles  to  the  telescope  by  perforating  the 
telescope  axis  and  covering  the  ends  with  glass  plates  as  described  in  the  preceding 
paragraph.  By  simply  sighting  through  the  axis,  offsets  may  be  conveniently  estab- 
lished without  disturbing  either  clamp  or  telescope  when  the  eye  is  brought  close  to 
the  instrument ;  its  application  is,  however,  limited  to  even  ground.  To  use  it  on  an 
uneven  ground  it  is  necessary  to  place  the  eye  at  a  distance  of  twelve  or  fifteen  inches 
from  the  instrument.  The  head  should  then  be  moved  until  the  eye  is  in  line  with  the 
openings  of  the  transverse  axis.  An  offset  can  then  be  aligned  irrespective  of  the  height 
of  the  instrument.  

Quick  Leveling  Attachment. 

This  we  can  apply  to  any  of  our  Mining  and  Mountain  Transits  and  Leveling 
Instruments.  It  adds  about  1  Ib.  to  the  weight. 


Protection  to  the  Object-Slide,  &c. 

A  rain  and  dust  guard  for  the  object-slide  is  now  furnished  with  all  of  our 
telescopes,  and  to  insure  smooth  working  of  the  object  slide  and  telescope  tube 
both  are  made  of  a  non-friction  metal.  The  graduation  of  the  horizontal  circle, 
the  centers  and  such  other  important  parts  that  are  liable  to  injury  by  the  action 
of  dust  and  water  in  the  field-use  of  an  instrument,  are  entirely  protected. 

General  Construction. 

In  regard  to  the  general  construction  of  pur  instruments,  the  dead  weight  Ls 
removed  wherever  it  is  shown  to  be  not  essential  to  the  stiffness  of  the  instrument ; 
but  we  have  at  the  same  time  strengthened  the  parts  most  likely  to  be  injured  by 
jtii  accident  or  fall.  Thus  the  base  of  the  standards,  the  vernier  plate  and  circle,  the 
parallel  plates  tor  leveling  screws,  the  telescope  axis,ihQ  flanges  of  centers,  cross-bar 
of  level,  etc.^  are  made  especially  rigid  and  provided  with  ribs.  Instead  of  finishing 
the  smaller  pieces  of  an  instrument  separately  and  then  joining  them  with  small 
screws,  or  solder,  each  screw  or  joint  being  a  weak  place  in  an  instrument,  we  have 
adopted  the  opposite  principle,  (at  an  increased  expense  to  us,)  and  aim  to  unite  as 
many  pieces  as  possible  in  a  single  casting,  which  casting,  by  means  of  ribs  is  made 
as  light  as  consistent  with  strength. 

We  also  call  attention  to  the  exceptionally  hard  bell-metal  and  phosphor  bronze 
used  for  our  centers  and  telescope  axis,  which  are  long  and  unyielding,  and  the 
remaining  parts  are  of  a  composition  metal,  which  is  itself  harder  than  hammered 
brass,  or  red  composition,  used  ordinarily  for  centers,  etc.  It  is  more  difficult  to 
work,  but  we  avoid  the  objectionable  softer  brass  in  its  use.  Experience  has 
proven  that  soft,  or  hammered  yellow  brass  is  unfit  for  a  good  field  or  astronomical 
instrument,  since  it  is  more  liable  to  fretting  and  yielding  generally,  and  in  the 
hammered  state  its  unequal  expansion  and  contraction  at  different  temperatures 
may  be  so  marked  as  to  impair  the  reliability  of  the  adjustments. 

Aluminum  bronze  containing  90%  copper,  is  also  extensively  applied  in  our  instru- 
ments on  account  of  its  great  tensile  strength. 

Aluminum  alloyed  with  small  percentages  of  silver  or  copper  must  be  used  with 
caution  on  account  of  its  softness.  (See  Aluminum  for  Instruments  of  Precision, 
page  23.) 


The  Finish. 

It  is  a  well-known  fact  that  the  black  lacquer  finish  has  one  objection,  It  absorbs 
the  heat  readily,  and  therefore  is  apt  to  expand  an  instrument  unequally,  and  thereby 
derange  its  adjustments.  We  therefore  consider  it  necessary  to  finish  certain  parts  of 
an  instrument  in  a  bright  but  not  glaring  finish  —  including  the  upper  plate  and  the 
telescope  in  the  transit ;  the  cross-bar  in  the  wye  level,  etc.  All  other  portions  may  be 
finished  and  bronzed  before  lacquering.  This  finish  gives  a  very  fine  appearance  to  the 
whole  instrument. 

Customers  desiring  to  have  their  instruments  finished  entirely  in  a  dark  metal  color, 
can  do  so  by  notifying  us  of  their  wishes. 

Our  Wear  Resisting  Leather  Finish. 

The  principle  is  borrowed  from  astronomical  instruments,  where  it  is  necessary  to 
cover  the  surfaces  with  some  non-conducting  material  in  order  to  avoid  disturbances 
in  instrumental  adjustments  caused  by  suddenly  varying  temperatures. 

We  have  adopted  this  principle  with  the  view  of  securing  the  same  results  for  our 
transits,  wye  and  dumpy  levels.  Some  of  these  levels  are  sensitive  to  a  depression  of 
a  single  second  of  arc. 

The  exterior  surfaces  of  our  instruments  so  finished  have  the  appearance  of  being 
covered  with  Morocco  leather  of  a  smooth  and  even  texture.  Its  close-grained  surface 
has  a  most  agreeable  and  soft  pliable  touch  to  the  hand,  and  eliminates  the  disagree- 
able feeling  experienced  when  metallic  surfaces  are  touched  in  very  cold  temperatures 
or  in  the  tropics. 

Instruments  finished  in  this  manner  heat  up  or  cool  down  very  gradually,  causing  a 
minimum  derangement  of  the  adjustments,  and  being  a  very  dark  color  this  finish 
unites  all  the  advantages  of  bright  lacquer  finishes,  with  the  convenience  ot  having  a 
dark  colored  instrument  for  use  in  the  field,  where  it  does  not  dazzle  the  eye  of  the  ob- 
server in  the  strongest  sunlight. 

Parts  so  treated  can  be  handled  with  impunity.  This  finish  is  impervious  to  damp- 
ness and  dryness,  or  mine  and  salt  water.  Dust  and  dirt  can  be  washed  off  and  candle 
grease  readily  removed.  Neither  will  it  fade,  nor  crack,  being  wholly  unlike  the  anti- 
quated cloth  finish  introduced  by  our  senior  member  in  1871.  It  is,  indeed,  entirely 
in  strict  keeping  with  our  products. 

It  is  difficult  to  determine  the  wearing  qualities  of  leather  and  cloth  finishes  of  sci- 
entific instruments.  A  good  finish  must  withstand  the  hard  usage  of  years.  The 
leather  finish  as  applied  to  our  instruments  was  thoroughly  tested  for  a  number  of  years 
before  being  applied  to  instruments  sent  out  on  orders. 

As  regards  durability,  it  is  quite  equal  to  the  bright  metal  finish,  and  is  superior  to 
bronze  or  black  metal  finished  surfaces.  This,  coupled  with  the  fact  that  it  can  be 
restored  at  any  time,  same  as  the  cloth  finish  formerly  applied  by  us  (to  which  latter  it 
is  incomparably  superior),  enables  us  to  unite  many  parts  of  an  instrument  into  one 
piece  or  casting  and  thereby  secure  greater  rigidity,  lightness  and  a  more  elegant  ap- 
pearance than  hitherto  attained  in  the  instruments  of  this  class  as  commonly  designed 
and  finished.  The  cloth  finish  heretofore  applied  will  be  used  only  to  a  very  limited 
extent. 

Packing. 

In  putting  our  instruments  in  their  cases,  none  of  them  separate  above  the  leveling 
screws.  They  stand  erect,  and  are  ready  for  use  upon  unlocking  the  case. 

The  cases  are  provided  with  rubber  cushions,  to  check  severe  jarring  arising  from 
transportation  over  rough  roads. 


10 

Care    of    Instruments.* 

Do  not  allow  the  legs  of  your  tripod  to  play  loose  on  the  tripod  head  ;  keep  nuts 
and  bolts  always  well  tightened  up  against  the  wood.  Examine  the  shoes  from  time 
to  time,  and  sharpen  them  if  necessary,  also  screw  the  shoes  tight,  if  wear  and  tear 
loosen  them.  Be  sure  your  instrument  is  well  secured  to  its  tripod  before  using  it. 
Bring  all  four  levelling  screws  to  a  seat  before  shouldering  instrument.  Let  the  needle 
down  upon  its  pivot  as  gently  as  possible,  and  allow  it  to  play  only  when  in  use  ;  if  too 
far  out  from  its  course,  check  movements  of  needle  carefully  by  means  of  lifter. 
Never  permit  playing  with  the  needle,  especially  not  with  knives,  keys,  etc.  Be  sure 
to  arrest  the  needle  after  use,  and  screw  it  well  up  against  the  glass  cover  before 
shouldering  the  instrument. 

As  a  rule  the  compass  needle  is  balanced  as  nearly  as  possible  for  the 
latitude  in  which  an  instrument  is  to  be  used.  If  only  a  trifle  out  do  not  meddle, 
inasmuch  as  one  can  do  more  harm  to  the  pivot  than  a  small  error  from  non-balancing 
would  amount  to,  but  if  the  compass  needle  requires  to  be  rebalanced 
proceed  as  follows: 

Remove  the  compass  glass  which  is  held  down  by  a  circular  ring  on  top  of  the 
glass,  which  may  be  removed  by  inserting  the  blade  of  a  knife  where  the  two  ends  of 
this  ring  come  together  and  prying  gently  upward.  By  means  of  a  piece  of  beeswax 
slightly  softened,  the  compass  glass  may  be  readily  lifted.  Then  raise  the  needle  up 
its  entire  length  by  means  of  the  lifter  and  carefully  remove  it  with  a  pair  of  tweezers. 
When  the  needle  is  balanced  it  should  be  as  carefully  placed  back  with  the  lifter  up 
as  before  to  retain  the  sharpness  of  the  pivot.  If  the  compass  glass  needs  to  be  re- 
moved entirely,  unfasten  the  two  screws  that  screw  the  stud  for  the  telescope  tangent 
screw  to  the  standards.  Don't  remove  the  telescope  from  its  wyes. 

Do  not  clean  the  glass  cover  or  the  lenses  with  a  silk  handkerchief ;  breathe  over 
the  compass-glass  and  reading  lens  if  one  is  used,  after  cleaning.  Examine  the  but- 
tons of  your  coat  with  regard  to  iron  that  may  be  concealed  in  them,  also  beware  of 
nickel-plated  watch  chains,  etc.  To  clean  the  object-glass  and  the  lenses  use  a  fine 
camel-hair  brush.  If  dust  or  sticky  or  fatty  matter  cannot  be  removed  with  the 
brush,  take  an  old  clean  piece  of  soft  linen,  and  carefully  wipe  it  off.  Do  not  unscrew 
the  object-glass  unnecessarily, —  this  is  apt  to  disturb  the  adjustment  of  line  of  colli- 
mation.  The  lens  nearest  the  eye  of  eye-piece,  as  well  as  the  front  side  of  the  object- 
glass,  need  careful  brushing  withjftne  brush  from  time  to  time. 

If  dust  settles  on  cross-hairs  and  becomes  troublesome,  unscrew  the  eye-piece  and 
object-glass,  and  gently  blow  through  the  telescope  tube,  cover  up  both  ends  and  wait 
a  few  minutes  before  inserting  the  eye-piece  and  object-glass.  Be  sure  to  have  the 
object-glass  cell  screwed  well  up  against  its  shoulder,  and  then  examine  the  adjustment 
of  line  of  collimation  (see  adjustment  of  line  of  collimation).  Do  not  grease  the  ob- 
ject-slide of  telescope,  or  screws  that  are  exposed  to  dust ;  use  a  stiff  tooth-brush  to 
clean  slides  or  threads  if  dusty. 

To  take  out  the  eye-piece,  unscrew  the  screw  at  the  end  of  the  main  tube,  take 
hold  of  the  eye-piece  and  pull  it  out. 

To  focus  the  cross-hairs,  take  hold  of  the  eye-piece  cap  and  turn  it  in  a  screw-like 
manner  until  cross-hairs  appear  distinct,  and  as  if  fastened  on  the  object  when  the 
head  is  being  moved. 

Should  there  bs  any  fretting  in  the  telescope  slide,  take  it  out,  and  endeavor  to 
smooth  the  rough  part  with  the  back  of  a  pocket  knife. 

If  the  focussing  slide  seems  to  work  too  hard,  everything  else  being  right,  4t 
is  generally  caused  by  the  lubricant  on  the  pinion  hardening  in  cold  weather,  and  the 
same  cause  may  also  make  the  focussing  slide  work  too  freely  in  hot  weather  by  soften- 
ing, i.  e.,  when  not  staying  in  place  when  in  a  vertical  position.  If  the  slide  moves 
too  freely  it  should  be  tightened  by  running  out  the  slide  to  its  full  length,  then  apply- 
ing a  screw-driver  to  the  screw  on  top  of  the  focussing  screw  and  turning  a  very  small 
part  oi  a  turn  until  the  required  friction  is  obtained.  If  the  slide  works  too  tightly 
run  in  the  slide,  unscrew  the  top  screw  one  turn,  gently  tap  it  by  the  screw-driver 
handle  to  release  it,  and  then  tighten  to  the  required  stiffness. 

To  prevent  the  focussing  slide  from  fretting,  usually  due  to  the  inrush  of  air  car- 
rying dust  and  grit  when  slide  is  being  run  out  causing  momentarily  a  rarefied  space, 
wrap  a  piece  of  chamois  skin  over  the  barrel  in  shape  of  tubular  form  and  fasten  by 
means  of  rubber  bands  or  sewing.  In  an  emergency  fine  watch-oil  may  be  used  to 
grease  the  slide  should  it  continue  to  fret,  until  the  instrument  can  be  sent  to  the 
maker. —  In  case  of  rain  during  non-use,  place  the  telescope  vertical,  object  end  up, 
and  no  water  can  enter  the  telescope. 

Never  use  emery  in  any  form  about  any  part  of  a  Transit  or 
a  t<evel,  whether  tangent  screws,  slides  or  centers.  If  anything  must  be  used,  a  very 
little  powdered  pumice-stone  mixed  with  fine  watch-oil  is  all  that  is  advisable,  and 
after  grinding,  then  clean  thoroughly.  The  uninitiated  are  advised  to  do  no  grinding 

*  For  additional  suggestions  see  p.  n. 


11 

whatever.  As  a  rule  more  harm  than  good  comes  to  the  instrument.  It  is  only  In 
case  of  emergency  that  such  heroic  treatment  should  be  resorted  to.  When  cleaning 
the  slide  and  inside  of  main  tube  great  care  must  be  taken  not  to  break  the  wires. 

To  focus  the  wires  sharply  turn  the  eye-piece  slightly  to  the  right  or  left 
as  the  case  may  be.  Remove  parallax  as  explained  on  page  54. 

To  clean  the  threads  of  leveling  or  tangent  screws  when  working  hard,  use  a  stifl 
tooth  brush  to  first  clean  the  threads  of  all  dust,  then  apply  a  little  oil,  and  work 
the  screw  in  and  out  with  alternate  brushing  to  remove  dirt  and  all  oil  until  it 
moves  perfectly  free  and  smooth. 

Screws  for  the  adjustment  of  cross-hairs  should  not  be  strained  any  more  than 
necessary  to  insure  a  linn  seat;  all  straining  of  such  screws  beyond  this  simply 
impairs  the  accuracy  of  instrument  and  reliability  of  adjustment. 

When  in  the  field  always  carry  a  Gossamer  water-proof  for  the  instrument  in 
your  pocket,  to  put  over  it  in  case  of  a  shower  or  dust  cloud.  On  reaching  office, 
after  use  of  instrument,  dust  it  off  generally  with  another  fine  brush ;  examine  the 
centers  and  all  other  principal  movements  to  see  if  they  run  perfectly  free  and 
easy,  and  oil  them  if  necessary ;  also  examine  the  adjustments.  This  will  save 
expense  and  many  hours  of  vexation  in  the  field. 


Care  of  Centers  and  Graduation. 

As  the  centers,  the  telescope  axis  and  the  graduations  require  greater  care  to 
preserve  their  fine  qualities,  perhaps  it  is  not  amiss  to  say  a  few  words  concerning 
their  treatment. 

Upon  finding  that  the  centers  do  not  revolve  as  free  as  usual  after  exposure  of 
the  instrument  in  an  extremely  hot  or  cold  weather,  they  should  be  cleaned  as  soon 
as  time  permits,  and  then  proceed  as  follows : 

Unscrew  the  milled-head  nut  at  the  extreme  end  of  the  cylindrical  tube  containing 
a  spiral  spring,  which  is  opposite  the  upper  tangent  screw.  Do  it  somewhat  cau- 
tiously, or  the  spring  will  fly  out.  Then  unscrew  a  small  cylindrical  case,  which 
also  has  a  milled  edge,  and  which  is  at  the  bottom  of  the  centers.  After  unscrewing 
the  nut  attached  to  the  inner  center,  a  gentle  pressure  upwards  will  lift  the  vernier  plate 
out  from  the  lower  part  of  the  instrument.  Take  a  fine  camel  hair  brush,  and  with  it 
clean  the  graduation,  the  verniers  and  the  inner  part  of  the  instrument, —  but  do  not 
rub  the  graduation,  especially  not  its  edge,  —  then  take  a  stick  of  about  the  same  taper 
as  the  inner  center,  wrap  some  wash-leather  slightly  soaked  in  fine  oil  around  it,  and 
clean  the  insides  of  the  sockets  as  carefully  as  possible;  then  remove  this  piece  of  wash- 
leather  and  wrap  a  fresh  piece  without  oil  around  the  stick  and  clean  dry.  Proceed 
similarly  with  the  centers  and  their  flanges. 

Before  applying  fresh  and  pure  watch  oil,  however,  care  should  be  taken  that 
not  a  particle  of  dust  or  other  foreign  matter  is  left  in  the  sockets,  on  the  centers, 
or  on  the  graduation.  This  caution  having  been  taken,  the  fresh  oil  should  be  well 
distributed  on  all  the  bearing  parts.  It  will  be  well  to  also  examine  the  arm  of  the 
clamp  screw  of  the  circle  and  telescope  axis,  and  if  necessary  clean  by  removing 
washer.  After  the  instrument  is  thoroughly  cleaned  and  oiled,  the  nuts  and  springs 
screwed  back  to  a  firm  seat,  the  instrument  must  turn  perfectly  free  and  yield  at 
the  slightest  touch  of  the  hand. 

To  remove  dirt  and  oxyd  that  may  have  accumulated  on  the  surface  of  a  solid 
silver  graduation,  apply  some  fine  watch-oil,  and  allow  it  to  remain  for  a  few  hours; 
take  a  soft  piece  of  old  linen  and  slightly  rub  until  drv,  but  without  touching  the  edge 
of  the  graduations.  If,  after  cleaning,  the  solid  silver  surface  should  show  alter- 
nately brighter  spots,  which  would  interfere  somewhat  with  the  accurate  reading  of 
the  graduation,  barely  moisten  the  finger  with  vaseline  and  apply  the  same  to  the 
surface;  then  wipe  the  finger  dry  and  lightly  rub  it  once  or  twice  around  the 
graduation.  Avoid  touching  the  edges  as  much  as  possible.  Such  cleaning,  however, 
must  only  be  resorted  to  when  absolutely  necessary,  and  then  only  with  the  greatest 
care,  as  it  is  too  apt  to  reduce  the  minuteness  of  the  graduation,  and  spoil  its  fine 
appearance.  If,  after  such  cleaning,  dirt  and  grease  has  accumulated  on  the  inner 
edge  of  the  graduation  and  verniers,  gently  wipe  clean  before  restoring  the  vernier- 
plate  to,  its  place.  Eemember,  also,  that  the  centering  of  the  graduations  of  the 
circle  and  verniers  is  a  most  delicate  adjustment  to  make.  These  should  never  be 
unscrewed  from  their  flanges  by  anybody  except  a  maker. 


12 

Care  of  Telescope  Lenses. 

As  dust  and  moisture,  as  well  as  perspiration  from  the  hands,  will  settle  on  the 
surface  of  the  lenses  of  a  telescope,  it  becomes  necessary  that  they  should  be 
cleaned  at  times.  A  neglect  to  keep  the  lenses  free  from  any  film,  scratches,  etc., 
greatly  impairs  the  claar  sight  through  the  telescope.  To  remove  the  dimness., 
produced  by  such  a  film,  proceed  thus :  —  Brush  each  lens  carefully  with  a  camel's 
hair  brush,  wipe  gently  with  a  clean  piece  of  chamois  leather  moistened  with  al- 
cohol, and  wipe  dry  using  a  clean  part  of  the  chamois  skin  on  every  portion  of  the 
lens,  to  avoid  grinding  and  scratching.  When  perfectly  transparent  brush  again 
to  remove  any  fiber  that  may  adhere  to  the  lens.  The  tubes  in  which  the  lenses  fit 
should  be  brushed,  and  if  damp  should  be  dried ;  this  done,  restore  each  lens  to 
its  original  place  as  marked.  To  remove  dampness  in  the  main  tube  of  the  teles- 
cope, take  out  the  eye-piece,  cover  the  open  end  with  cloth  and  leave  the  instrument 
in  a  dry  room  for  some  time. 

If  an  instrument  has  been  exposed  to  a  damp  atmosphere,  or  water  has  pene- 
trated the  telescope,  moisture  may  settle  between  the  crown  and  flint  glass  of 
which  the  object-glass  is  composed.  If  such  is  the  case  expose  the  instrument  to 
the  sun  for  a  few  hours,  but  if  in  the  winter,  leave  it  in  a  warm  room  some  distance 
from  the  stove,  the  moisture  will  then  generally  evaporate.  However,  if  not  suc- 
cessful, unscrew  the  object-glass  from  the  telescope,  and  heat  it  slightly  over  a 
stove  or  open  fire.  If  a  film  settles  between  these  glasses  nothing  can  be  done  ex- 
cept sending  the  instrument  to  the  maker.  The  two  glasses  form  one  lens  only 
and  must  not  be  disturbed,  as  upon  their  relation  to  each  other  the  definition  and 
achromaticity  of  the  telescope  depends.  Much  depends  also  on  the  stability,  with 
which  these  lenses  are  mounted  in  their  cell,  as  any  looseness  between  them  or  the 
cell  will  affect  the  adjustment  of  line  of  collimation.  —  Of  course,  if  at  any  time  the 
object-glass  has  been  unscrewed  from  the  telescope,  this  latter  adjustment  must 
again  be  verified  before  the  instrument  is  used. 

Additional     Instructions    concerning    the    Care    of 
Telescope    Lenses,   etc. 

Ever  since  the  introduction  of  the  high  power  in  the  telescopes  of  geodetic  in- 
struments,  now  used  by  the  best  makers,  complaints  are  frequently  made  of 
the  loss  of  light  in  such  telescopes  and  of  the  hazy  appearance  of  objects 
viewed  through  the  in,  the  latter  in  particular  when  an  instrument  has  seen  service 
in  the  field  for  some  time.  Now,  while  the  loss  of  light  is  wholly  due  to  the  greater 
power  as  compared  with  the  low  powers  formerly  in  vogue,  and  to  the  use  of  erect- 
ing eye-pieces  (see  page  31),  the  "haziness"  is  produced  principally  by  films 
of  dirt,  settled  on  or  between  the  lenses  of  a  telescope,  and  becomes  even  more 
marked  as  more  lenses  are  used  in  a  telescope. 

Perhaps  it  is  proper  to  say  here,  that  when  comparisons  are  made  between  low 
and  high-powered  telescopes  of  geodetic  instruments,  other  things  being  equal,  the 
first  named,  as  a  rule,  will  incite  favor,  because,  as  in  spy-glasses,  the  image  of  an 
object  seen  through  them  has  a  brilliancy  never  attained  by  telescopes  of  higher 
power.  But,  whenever  the  results  of  stadia  work,  or  fine  levelling,  as  obtained  with 
the  more  powerful  telescope,  are  compared  with  those  obtained  by  a  lower  power, 
it  will  be  found  that,  though  less  brilliant,  the  defining  power  of  a  high-powered 
telescope  is  superior  to  the  other  within  the  customary  range  of  distances  had  in 
the  ordinary  engineer's  and  surveyor's  practice, 

On  the  other  hand,  owing  to  the  less  amount  of  light  with  high  powers,  it  is 
necessary  that  the  fine  qualities  of  the  superior  lenses  required  for  them  should  be 
preserved,  and  on  this  account  a  more  frequent  inspection  and  a  more  careful 
treatment  of  them  is  needed  than  when  lower  powers  are  used, — inasmuch  as  the 
least  impairment  of  these  lenses  by  films,  or  dust,  etc.,  will  reduce  the  defining 
power  accordingly.  A  little  extra  care,  as  consequent  upon  the  use  of  high-powered 
lenses,  is,  therefore,  imperative,  but  in  so  doing  one  is  more  than  compensated  by  the 
satisfaction  of  having  a  finer  and  more  penetrating  telescope. 

To  prevent  an  untimely  settling  of  a  film  on  the  lenses  of  a  telescope,  and  par- 
ticularly that  apt  to  form  on  the  inner  surfaces  of  the  lenses  composing  an  object- 
glass  that  has  not  been  cemented  together  —  such  film  being  so  fatal  in  an  object- 
glass  because  it  cannot  ordinarily  be  reached  and  without  disarranging  the  cross-wire 
adjustments — the  treatment  of  an  instrument  should  be  strictly  in  accordance  with 
the  instructions  given  under  "  Prevention  better  than  Cure,"  page  17.  Unless  these 
conditions  are  complied  with,  the  greater  efficacy  of  a  telescope  composed  of  supe- 
rior lenses  will  be  entirely  lost. 

Upon  finding  that,  after  carefully  cleaning  the  object-glass  and  the  lenses  of  the 
eye-piece,  the  telescope  is  not  as  clear  as  when  first  received  from  the  maker,  then 
the  cause  of  it  is  generally  a  film  between  the  lenses  of  the  object-glass  — wo  take 
for  granted  that  the  lenses  are  not  scratched  or  otherwise  impaired — but,  as  a  rule, 
it  takes  several  years  (with  carelul  use  sometimes  many  years)  before  such  a  film 


13 

has  sufficiently  developed  to  impair  the  transparency  of  these  lenses.  J3ut  when- 
ever it  is  found  that  a  film  has  settled  between  them,  then  it  is  best,  if  the  distance 
is  not  too  great,  to  send  the  whole,  instrument  to  its  maker,  and  if  this  is  not  feasible, 
then  the  telescope,  at  least,  well  and  soft  packed  in  a  box,  should  be  sent. 

Cemented  Object-glasses. —  To  prevent  the  settling  of  a  film  between  the 
lenses  composing  an  object-glass,  and  to  avoid  disturbing  reflections  of  light  from 
their  inner  surfaces,  such  films  and  reflections  imparting  to  an  object  viewed 
through  a  telescope  the  hazy  appearance  noticeable  in  high-powered  telescopes, 
we  now,  since  1889,  cement  these  lenses  together,  so  as  to  form  one  lens  only.  The 
lenses  so  treated  are  more  efficacious  in  many  respects  than  when  separated  by 
three  thin  pieces  of  tin  foil,  as  has  been  the  custom  of  nearly  all  instrument 
makers  up  to  date. 

The  cement,  however,  needs  some  five  or  six  months  to  harden,  and  until  it  has 
hardened  sufficiently,  an  exposure  to  a  cold  atmosphere  causing  a  greater  contrac- 
tion of  the  metal  cell  than  the  glass,  the  lenses  are  very  apt  to  warp,  which  may 
lead  to  a  distortion  of  an  object,  when  viewed  through  such  an  objective. 

The  proper  treatment  of  an  object-glass  freshly  cemented  is  to  keep  the  instru- 
ment, when  not  in  use,  in  a  room  having  a  mean  temperature  of  about  68°  F.,  or 
slightly  above.  The  same  treatment  should  be  followed  if  it  is  found  that  the 
image  formed  of  an  object  is  slightly  distorted ;  only  in  this  case  the  temperature 
in  which  it  is  kept  over  night  should  be  raised  to  about  75°  or  80°  F.  This  treat- 
ment applies  only  to  normally  mounted  objectives.  If  they  are  too  tightly  fitted 
the  lenses  cannot  be  restored  to  their  original  efficacy  without  being  attended  to  by 
a  maker. 

Object-glasses  that  are  cemented  are  very  apt  to  show  some  specks,  or,  with  ill 
usage,  cracks  in  the  cement,  but,  unless  the  specks  are  very  numerous,  so  as  to 
cover  almost  the  whole  area  of  the  object-glass,  the  opacity  caused  by  them  does 
not  sensibly  affect  the  efficacy  of  the  telescope,  and  there  core  need  not  disturb  the 
mind.  Our  experience  is  that  the  usefulness  of  an  instrument  is  greatly  enhanced 
when  these  lenses  are  cemented  together,  and  that  a  few  specks  that  may  appear 
after  an  exposure  from  a  sudden  change  from  hot  to  a  very  cold  atmosphere,  or  vice 
versa,  are  a  lesser  evil,  as  compared  with  the  ill  effects  produced  by  a  film  that  in 
time  will  settle  between  these  lenses  if  separated  by  pieces  of  tin  foil,  or  even  when 
brought  in  direct  contact  with  each  other,  as  such  a  film  will  have  much  the  same 
effect  as  a  fog,  in  preventing  vision. 

When,  after  carefully  cleaning  the  lenses  of  a  telescope,  the  object-glass  of  which  has 
its  lenses  separated  by  pieces  of  tin  foil,  it  is  found  that  the  image  is  not  as  clear  as 
originally,  it  is  a  sure  sign  that  there  is  a  film  between  its  lenses,  and  that  it  has  been 
exposed  to  a  damp  or  impure  atmosphere,  either  by  injudicious  use  in  the  field,  or  by 
being  left  too  long  a  time  in  the  packing  box,  in  which  it  is  protected  by  cushions  of 
paper  or  shavings,  both  of  which  attract  moisture,  or  by  storing  it  away  in  its  box  in 
such  an  improper  place  as  a  basement  or  cellar.  Such  film  being  noticed,  it  will  then 
be  well  to  send  the  object-glass,  or  much  better,  the  telescope,  or,  best,  if  the  distance  is 
not  too  great,  the  whole  instrument,  to  the  maker,  in  order  that  the  lenses  may  be 
cleaned  by  him,  and,  if  deemed  advisable,  be  cemented.  The  slight  expense  incurred 
of  a  few  dollars  will  be  more  than  justified  by  the  advantage  gained. 

When  the  object-glass,  or  telescope  is  returned  after  the  cleaning  or  cementing  of 
its  lenses,  the  cross-wire,  spirit  level,  and  vertical  arc  adjustments  of  the  instrument 
will  require  a  thorough  verification  before  it  should  be  used.  In  case  the  whole  instru- 
ment has  been  sent  to  the  maker,  these  adjustments  are  attended  to  by  him.  If  the  ob- 
ject-glass has  been  cemented,  the  telescope  should  be  watched  for  a  year  to  see  that  there 
is  no  distortion  of  the  image.  If  there  is  a  distortion,  it  will  indicate  that  the  object- 
glass  has  been  too  tightly  fitted,  of  which  fact  we  should  be  informed,  as  also  whether 
after  cementing  the  object-glass  the  instrument  retains  its  cross-wire  adjustment  the 
same  as  before  the  cementing  took  place.  If  the  cross-wire  adjustments  have  to  be 
more  frequently  made  than  before  the  lenses  were  cemented,  it  indicates  that  the  object- 
glass  is  not  tightly  fitted  to  its  cell ;  and  if  such  is  the  case  it  should  .be  sent  to  us  to  be 
more  tightly  fitted,  after  a  lapse  of  about  ten  or  twelve  months,  when  the  cement  will 
have  sufficiently  hardened  to  allow  of  a  tighter  fit  of  the  object-glass  in  its  cell. 

In  telescopes  of  very  high  power  it  is  of  as  great  importance  to  keep  the  lenses  of  the 
eye-piece  free  from  grit  and  films  as  of  the  object-glass.  Therefore,  whenever  the  tele- 
scope does  not  appear  to  be  clear,  the  lenses  of  the  eye-piece  need  most  careful  cleaning 
(if  necessary,  every  four  weeks).  The  cleaning  must  be  done  by  first  wiping  gently 
with  a  clean  piece  of  old  linen  barely  moistened  with  alcohol  and  then  wiping  dry,  using 
a  clean  part  of  the  linen  on  every  surface  of  the  lenses.  (Please  read  the  various 
articles  on  this  point  on  pages  10,  11  ,and  31,  of  our  handbook  and  catalogue.)  To  re- 
move the  eye-piece,  unscrew  the  German-silver  screw  at  the  eye-end  of  the  telescope.  — 
Of  course,  after  cleaning,  every  lens  must  be  put  back  in  its  tube  precisely  as  marked, 
and  then  the  outer  bearings  of  the  eye-piece  in  the  main  tube  must  be  greased  with 
tallow  before  the  German-silver  screw  is  restored  to  its  place. 


14 

Additional  Suggestions  Pertaining  to  the  Care  and  Pro* 
tection  of  Instruments  in  Field  Use. 

In  field  use,  an  instrument  has  to  be  necessarily  exposed  to  the  heat  of  the  sun, 
and  to  the  action  of  dust  and  water;  all  of  these,  however,  singly  or  combined,  ha/e 
a  tendency  to  affect  its  accuracy  and  endurance.  While  our  instruments  in  particular 
have  been  designed  to  guard  against  injuries  resulting  from  exposure  of  this  kind, 
yet  glaring  abuses,  such  as  to  allow  it  to  stand  for  hours  in  the  hot  sun,  etc.,  without  a 
covering  or  shelter  of  some  sort,  may  often  lead  to  a  permanent  injury  to  its  most  vital 
parts.  To  preserve  the  finer  qualities  of  an  instrument,  viz.,  the  telescope  slide,  the 
lenses,  the  edge  of  the  graduation  and  verniers,  the  centers,  etc.,  any  undue  unequal 
expansion  of  the  different  parts  should  be  prevented.  A  bag  thrown  over  the  instru- 
ment when  not  in  use,  or  any  shelter  that  can  be  had,  is  to  be  recommended.  Wi  ile 
in  use,  an  umbrella  or  screen  held  over  it  will  insure  greater  permanency  of  its  ad- 
justments, and  the  results  obtained  will  be  more  accurate  and  uniform  than  when 
carelessly  exposed. 

To  protect  an  instrument  from  the  effects  of  salt  water,  when  used  near  the  sea 
coast,  a  fine  film  of  watch-oil  rubbed  over  the  exposed  parts  will  often  prevent 
the  appearance  of  oxyd.  To  remove  such  oxyd-spots  as  well  as  possible,  apply 
some  watch-oil  and  allow  it  to  remain  for  a  few  hours,  then  rub  dry  with  a  soft  piece 
of  linen.  —  To  preserve  the  outer  appearance  of  an  instrument,  never  use  anything  for 
dusting  except  a  fine  camel's  hair  brush.  To  remove  water  and  dust  spots,  first  use 
the  camel's  hair  brush,  and  then  rub  off  with  fine  watch-oil,  and  wipe  dry  ;  to  let  the 
oil  remain  would  tend  to  accumulate  dust  on  the  instrument. 

Lubricating,  etc.  —  An  instrument  used  in  a  tropical  or  semi-tropical  country, 
or  during  the  warm  season  in  a  northern  latitude,  requires  more  frequent  cleaning, 
and  oiling  than  in  the  more  temperate  climes  and  seasons ;  but  so  long  as  an  instru. 
ment  works  well  and  the  centers  revolve  freely,  it  is  best  not  to  disturb  it.  However, 
If  necessary,  proceed  as  described  under  "Care  of  Centers,  etc."  A  few  additional 
remarks  we  give  here :  Should  the  centers  or  the  object-slide  commence  to  fret,  they 
should  be  examined  as  soon  as  possible.  Once  commencing  to  fret,  it  grows  worse  rapidly 
and  oftentimes  is  then  beyond  repairing.  Never  use  emery  or  emery-paper  on  them,  as 
this  will  cause  everlasting  trouble  afterwards.  After  a  thorough  cleaning  of  the  slide 
and  tube  (taking  care  not  to  break  the  cross-wires},  endeavor  to  smooth  carefully 
the  injured  parts  with  the  back  of  a  pen-knife,  ana  barely  apply  enough  tallow  to 
grease  the  surface  of  the  injured  part.  If  this  does  not  remove  the  trouble,  a  little 
scraping  of  the  roughened  parts  on  the  slide,  and,  if  accessible,  on  the  inside  of  the 
tube,  may  become  necessary,  and  apply  a  mere  trifle  of  finely-powdered  pumice 
stone  moistened  with  oil.  Replace  the  slide  and  grind  a  little  by  moving  it  in  and 
out;  clean  thoroughly,  and  with  a  piece  of  charcoal  moistened  with  oil  smooth  the  parts 
thus  ground  on  the  slide.  This  process  of  grinding  is  a  most  precarious  operation, 
and  generally  requires  the  hand  of  a  skillful  workman;  it  should  be  resorted  to  only 
in  case  of  utmost  necessity.  Whenever  permissible,  recourse  should  be  had  to  a 
maker.  These  remarks  apply  equally  to  the  centers. 

The  centers  of  a  transit  should  always  be  lubricated  with  fine  watch-oil  only,  and 
after  a  careful  cleaning;  never  apply  fresh  oil  before  thoroughly  wiping  off  old 
grit  and  oil.  Rendered  marrow  is  a  most  excellent  lubricant  for  instruments  made  o\ 
brass  and  the  many  kindred  alloys  of  copper  and  tin.  In  the  varying  climes  of  oui 
northern  latitudes  this  lubricant  becomes  rigid  in  cold  weather,  and  an  instrument  so 
treated  will  often  become  unmanageable  in  the  field.  Its  application,  particularly 
to  the  centers  of  a  transit,  is  therefore  restricted  to  the  wanner  zones.  The  use  of 
watch-oil  for  the  finer  parts  of  an  instrument,  involving  freedom  of  motion,  is 
imperative  in  our  latitudes. 

Many  parts  of  an  instrument,  especially  those  whose  metal  compositions  are 
closely  related  to  each  other,  may  sometimes  cause  trouble  if  simply  oiled.  If  they 
begin  to  fret  and  grind,  but  are  otherwise  free  from  grit,  etc.,  the  judicious  application 
of  a  little  marrow  may  prove  very  beneficial,  but  it  should  be  cleaned  off  again  as 
much  as  possible.  The  rack  and  pinion  motion  and  the  telescope  clamp  should 
always  be  greased  with  marrow,  but  the  clamp,  tangent  and  leveling  screws,  should 
receive  as  little  of  it  as  possible  in  the  Northern  States. 

Vaseline,  not  having  as  great  a  tendency  to  rigidity  under  similar  circumstances, 
may  prove  an  excellent  substitute  for  marrow,  and  may  often  be  applied  to  level- 
oenters,  where  watch-oil  would  not  give  the  necessary  rigidity  in  the  use  of  the  more 


15 

ordinary  instruments,  but  it  must  be  renewed  quite  often.     In  the  finer  class  of 
leveling  instruments,  the  centers  should  be  lubricated  with  oil  only,  as  in  transits. 

A  great  deal  of  annoyance  is  caused  to  the  engineer  if  the  eye-piece  or  the  object- 
slide  of  the  telescope  move  too  freely  in  their  tubes,  requiring  a  re- focussing  of  the 
cross-wires  and  object  at  every  revolution  of  the  telescope  in  altitude.  If  the  eye- 
piece can  be  retained  in  its  socket,  with  sufficient  friction  to  keep  it  focussed  to  the 
cross-wires,  no  matter  how  much  it  may  wabble  otherwise,  this  imperfection  (in  old 
instruments)  will  not  lead  to  any  inaccuracy,  but  if  there  is  not  sufficient  friction  to 
keep  it  focussed  to  the  wires,  a  little  rendered  tallow  or  marrow  applied  to  its  bearing 
surfaces  in  most  cases  will  remedy  this  evil.  Wabbling  in  the  object-slide,  however, 
leading  to  inaccuracy  of  collimation,  or  back-lash  in  its  rack  or  pinion  motion,  can  be 
remedied  only  by  a  maker;  but  if  the  object-slide  moves  too  freely  in  and  out  of  its 
tube  only,  this  may  be  remedied  by  applying  a  little  tallow  to  the  bearing  parts  of 
the  rack  and  pinion,  or  by  tightening  the  screw  in  the  pinion-head.  If  not  entirely 
successful,  a  thin  disk  made  of  parchment,  or  a  thin  leather-washer,  both  greased 
with  tallow,  and  inserted  between  the  flanges  of  the  pinion-head  and  its  socket, 
will  insure  the  desired  result.  —  These  latter  remarks  apply  to  transit  and  level 
telescopes  of  the  customary  design.  In  telescopes,  where  the  object-glass  is  mounted 
permanently  to  the  telescope-tube,  the  eye-piece  tube,  containing  the  cross-wires, 
becomes  the  slide  with  which  to  focus  the  object.  Its  motion  must  be  in  a  line 
parallel  to  the  optical  axis.  Any  wabbling  in  this  eye-piece  slide  would  lead  to  in- 
accuracy in  sighting  through  the  telescope,  hence  it  requires  the  most  careful 
treatment  on  the  part  of  the  engineer. 


Care  in  the  Use  of  Spirit-Levels. 

Spirit-levels  are  very  susceptible  to  the  least  change  in  temperature,  as  will  be 
readily  seen  by  the  difference  in  the  length  of  its  bubble  in  varying  temperatures. 
Hence,  to  guard  against  inaccuracies  from  this  source,  it  is  necessary  that  the 
bubble  should  lengthen  symmetricallv  from  the  center  of  its  graduated  scale  (sup- 
posed to  be  made  by  the  maker),  and  that  both  of  its  ends  should  be  read.  Suffi- 
cient time  must  also  be  allowed  for  the  bubble  to  settle  before  a  reading  is  made. 

The  fluid  ordinarily  used  for  levels  is  pure  alcohol,  and  requires,  according  to 
curvature,  diameter  and  length  of  tube  and  length  of  bubble,  from  twenty  sec- 
onds to  one  minute  to  attain  its  equilibrium.  The  composition  fluid  used  in  our 
levels  for  field  instruments  requires  only  from  five  to  fifteen  seconds  of  time ;  those 
filled  with  pure  ether,  a  few  seconds  only. 

A  great  source  of  error  in  spirit-levels,  however,  increasing  with  their  greater 
sensitiveness,  is  occasioned  by  an  unequal  heating  of  the  level-tube,  as  the  bubble 
will  always  move  towards  the  warmer  spot  or  end,  thereby  imparting  to  the  instrument 
an  inaccurate  position.  This  must  be  attributed  to  a  changed  condition  in  the 
adhesiveness  of  the  fluid  in  the  level-tube,  and  not  to  a  change  in  the  form  of 
the  tube  itself.  Therefore,  to  guard  against  inaccuracy  resulting  from  sudden 
changes  of  temperature,  a  spirit-level,  while  in  use,  should  be  protected  from  the 
sun,  and  no  part  of  it  or  its  mounting  should  ever  be  touched  with  bare  fingers ; 
neither  should  it  be  breathed  upon,  nor  the  face  of  the  observer  come  too  close  to 
it.  For  this  reason,  in  the  finer  instruments  the  mountings  of  our  spirit-levels 
are  cloth- finished,  and  if  the  levels  are  detachable  they  are  provided  with  wooden 
handles,  as  the  case  may  require,  and  glass  covers  are  placed  over  them  whenever 
deemed  necessary. 

If  at  any  time  during  the  progress  of  field-work  a  spirit-level  has  been  improperly 
exposed,  it  is  best  to  cover  it  with  a  cloth  for  from  five  to  fifteen  minutes,  before 
proceeding  with  further  work. 

Mounting  Spirit  Levels.  —  To  prevent  any  undue  strain  and  change  of 
curvature  in  spirit  levels  used  in  astronomical  instruments,  they  are  mounted  by  us 
in  wyes,  as  shown  in  the  cuts  of  these  instruments,  and  are  protected  from  injury,  or 
inaccuracy  caused  by  the  breath  of  the  observer  and  other  air  currents,  by  a  cover 
of  glass  placed  over  them.  Such  a  mounting,  while  most  suitable  for  such  dslicate 
levels,  would,  however,  require  constant  attention  and  expose  a  spirit  level  to  break- 
age in  field  instruments.  To  guard  against  this  danger  and  to  lessen  the  expense 
wid  weight,  the  spirit  levels  for  field  instruments  are  mounted  in  a  brass  tube;  but 


16 

owing  to  the  difference  existing  in  the  expansion  and  contraction  of  glass  and  brass 
at  diiferent  temperatures,  a  spirit  level  so  mounted  may  sometimes  become  loose,  in- 
volving inaccuracy  and  unreliability  of  adjustment.  —  Upon  finding  that  the  adjust- 
ment of  a  spirit  level  in  an  even  temperature  is  not  as  stable  as  desirable,  the  level 
fastenings,  tube,  screws,  etc.  should  be  examined,  to  see  if  any  of  them  are  loose.  If 
the  trouble  is  in  the  screws,  tighten  them  up;  but  if  the  spirit  level  can  be  shifted  in 
its  tube  by  a  touch  of  the  finger,  take  it  apart ;  soften  the  plaster  of  paris  in  water, 
and  remove  it  with  a  sharp  pointed  stick  of  wood.  Cautiously  move  the  spirit  level 
with  your  finger,  at  first  only  a  trifle  to  and  fro,  increasing  the  length  of  stroke  little 
by  little,  until  it  can  be  safely  taken  out  without  breaking;  —  clean  thoroughly.  Cut 
pieces  of  white  paper,  of  the  width  of  the  radius  of  the  tube,  and  somewhat  shorter 
than  the  length  of  the  spirit  level,  but  longer  than  the  opening  in  the  brass  tube,  and 
insert  these  of  sufficient  quantity  at  the  bottom  of  the  brass  tube,  to  fill  up  the  space 
intervening  between  the  glass  and  the  brass  tube.  The  uppermost  layer  of  paper 
should,  however,  be  so  wide,  as  to  envelope  the  spirit  level  up  to  the  opening  in  the 
brass  tube.  Now  insert  the  spirit  level,  taking  care  not  to  touch  the  glass  ends  that 
are  sealed  up,  and  place  the  division  or  other  marks,  indicating  wh  ire  the  level  has 
been  ground  to  a  true  curvature,  uppermost  in  the  brass  tube.  The  level  must  be 
pushed  in  with  sufficient  friction  to  prevent  slipping  in  the  tube,  yet  not  so  tight  as 
to  cause  a  crack  at  a  subsequent  low  temperature,  as  brass  will  contract  more  than 
glass.  No  part  of  the  spirit  level  should  touch  any  part  of  the  metal  tube.  Now 
prepare  some  plaster  of  paris  with  water,  of  the  consistency  of  paste,  and  pour  in  at 
each  end  enough  to  fill  up  the  space  between  the  end-pieces  and  the  glass,  stirring 
it  sufficiently  to  make  a  perfect  contact  by  it  and  the  glass  and  the  brass,  but  leaving 
the  spirit  level  ends  exposed.  Now  put  the  level  together,  and  adjust  as  described 
elsewhere. 

There  are  other  causes,  such  as  centers  and  flanges  that  have  been  bent  by  falls, 
etc.,  or  that  have  been  worn  out  —  unequal  expansion  or  contraction  in  different  tem- 
peratures of  the  metals  employed  in  the  construction  of  an  instrument,  or  a  non- 
symmetrical  lenghtening  or  shortening  of  the  air-bubble  at  different  temperatures  — all 
of  which,  singly  or  combined,  tend  to  impair  the  adjustment  of  spirit  levels  on 
Instruments.  Of  these  we  will  not  speak  here,  as  it  requires  a  most  thorough  mecha- 
nician and  instrument-maker  to  trace  the  cause  to  its  proper  source. 

Being  assured  that  the  level  is  mounted  as  explained  above,  our  advice  is,  not  to 
meddle  too  frequently  with  the  adjustment  of  a  spirit  level.  Though  it  may  appear 
to  be  out  one  day.  it  may  be  in  perfect  adjustment  other  days.  It  is  the  function  of 
a  spirit  level  to  indicate  the  changes  taking  place  in  an  instrument,  so  that  the 
engineer  may  make  proper  allowance  and  apply  his  corrections,  as  the  character  of 
his  work  may  require.  The  finer  an  instrument,  the  more  sensitive  the  spirit  levels 
must  be,  in  order  to  admit  of  corrections  to  arrive  at  closer  results.  As  a  rule,  a 
spirit  level  that  does  not  indicate  changes  taking  place  in  an  instrument,  is  too  in- 
sensitive for  the  character  of  the  instrument,  and  in  many  cases  entirely  unfit  fof 
reasonably  good  work. 


Replacing   Broken   Cross- Wires. 

The  cross-lines  in  our  telescopes  are  bonajtde  spider  webs  (except  where  plati 
num  wires  have  been  specially  ordered).  In  case  they  should  be  broken,  they  may 
be  restored  in  the  following  manner :  clean  the  reticule  frame  of  all  foreign  matter ; 
put  it  on  a  sheet  of  white  paper  with  the  cuts  on  its  surface  uppermost.  Prepare  a 
little  shellac  by  dissolving  it  in  the  best  alcohol  and  waiting  until  it  is  of  the  con- 
sistency of  oil.  From  the  spider's  cocoon,  (those  from  a  small  black  wood-spider 
preferred),  which  the  engineer  has  prudently  secured  at  some  previous  time,  select 
two  or  three  webs,  each  about  two  inches  long  and  of  the  same  appearance.  Attach 
each  end  of  these  webs  to  a  bit  of  paper  or  wood  to  act  as  weights,  and  immerse 
them  in  water  for  five  or  ten  minutes.  Remove  one  web  from  the  water,  and  very 
gently  pass  it  between  the  fore-finger  and  thumb  nails,  holding  it  vertically  to  re- 
move any  particles  of  moisture  or  dirt.  Stretch  the  web  carefully  over  two  of  the 
opposite  cuts  in  the  reticule  frame.  Fasten  one  end  by  a  drop  of  the  shellac,  —  let 
fall  gently  from  a  bit  of  pointed  wood  or  the  blade  of  a  penknife.  Wait  a  moment 
lor  this  drop  of  shellac  to  harden.  See  that  the  web  is  stretched  tight  across  the 


17 

frame,  and  apply  another  drop  of  the  shellac  to  the  opposite  cut  with  its  enclosed 
web.  Wait  several  minutes  before  cutting  off  the  two  ends  of  the  web,  and  then 
proceed  in  the  same  manner  with  the  web  which  is  to  be  placed  at  right  angles  to 
this  one. 

NOTE.  —The  fine  spider-threads  used  were  tormerly  taken  from  the  cocoons  of  the  small  black  wood-spider; 
now,  however,  we  obtain  them  from  the  cocoons  of  a  species  of  spider  found  in  Michigan.  These  threads  ar* 
almost  opaque,  and  not  apt  to  relax  their  tightness  if  properly  placed  on  the  diaphragm,  and  as  they  retain  their 
elasticity,  they  are  preferable  to  platinum  wires,  which  have  a  tendency  to  break,  owing  to  their  great  brittle- 
ness.  The  best  spider-threads  are  those  of  which  the  spider  makes  its  nest.  These  nests  are  yellowish-brown 
balls,  which  may  be  found  hanging  on  shrubs,  etc.  ,  in  the  late  fall  or  early  winter.  The  nest  should  be  torn  open  and 
the  eggs  removed  ;  if  this  is  not  done,  tne  young  spiders,  when  hatched,  will  eat  the  threads.  The  fibers  next  to  the 
eggs  are  to  be  preferred  on  account  of  their  fineness  and  darker  color.  As  it  is  important  to  get  the  proper  kind 
of  spider-web,  we  subjoin  an  extract  from  a  letter  addressed  to  us  on  the  subject  by  Prof.  J.  B.  Davis,  Uni- 
versity of  Michigan,  Ann  Arbor,  Mich.,  to  whom  we  are  indebted  for  our  supply. 

"  The  species  of  spider  of  which  I  send  you  cocoons  is  not  difficult  to  find  in  Ann  Arbor  —  Lat.  42°  26'  N. 
—  as  far  as  my  experience  goes,  and  is  numerous  on  Beaver  Island,  out  in  Lake  Michigan  —  about  46°  N.  —  at 


the  high 

£iite  numerously,  as  I  am  led  to  think  it  is  quiet  rather  than  security  this  spider  seeks.  The  body  of  the  female 
three-fourths  of  an  inch,  I  guess,  long,  and  nearly  half  an  inch  wide  across  the  abdomen.  The  male  is  about 
the  same  length,  but  far  slimmer.  They  are  both  entirely  harmless.  I  never  knew  any  one  to  get  bitten  by 
either,  and  many  persons  in  my  observation  have  had  them  freely  crawling  over  their  hands,  face  and  body. 
They  may  be  certainly  gently  handled  without  the  least  harm.  They  both  (male  and  female)  bear  a  plain 
escutcheon  design  on  the  back  of  the  abdomen;  female  much  the  more  beautiful,  —  in  browns.  Colors  all 
brown  and  yellowish  brown.  The  cocoon  is  a  snarl  of  webs,  and  is  attached  under  ledges  of  window-sills,  cor- 
nices, projections  of  gables,  and  the  like  partly  sheltered  places.  The  color  of  the  threads  you  have  is  of  a  light 
corn-color,  distinctly  separating  it  from  the  white  cotton-like  cocoons  so  common  everywhere.  The  threads  are 
silky,  not  like  cotton.  Of  late  years  I  keep  one  or  two  nice  cocoons  where  they  can  be  reached.  You  know  out 
can  wrap  them  in  a  bit  of  paper  and  carry  them  in  the,  pocket,  or  any  such  place,  and  they  are  always  ready." 


Prevention  Better  than  Cure. 

IT  cannot  be  denied  that  instruments  frequently  meet  with  serious  accidents 
which,  with  a  little  care  on  the  part  of  the  operator,  could  be  prevented.  It  cer- 
tainly does  not  betoken  proper  care  to  leave  it  standing  unguarded  in  a  street,  road, 
or  pasture,  or  in  close  vicinity  to  blasting,  or  to  expose  it  unnecessarily  to  the  burning 
rays  of  the  sun,  or  to  dust,  dampness,  or  rain  at  any  time.  Such  carelessness  must 
inevitably  result  in  deterioration  of  the  accuracy  and  efficiency,  not  to  speak  of  the 
durability,  of  an  instrument. 

It  should  be  borne  in  mind  that  there  are  many  parts  of  an  instrument  which,  if 
once  impaired,  cannot  be  restored  to  their  original  efficiency ;  and  when  it  is  consid- 
ered that  a  conscientious  maker  bestows  no  little  care,  time,  and  expense  on  his 
work  in  order  to  attain  a  high  degree  of  perfection,  such  neglect  seems  like  a 
wanton  waste  of  human  energy  and  skill. 

Legs  of  tripods,  if  fitting  too  loose  or  too  tight,  and  dull  shoes  are  frequent 
sources  of  falls,  and  loose  shoes  tend  to  make  an  unsteady  instrument.  The  test 
of  the  proper  degree  of  the  tightness  of  the  legs  is  this,  that  if  the  leg  is  raised  to  a 
horizontal  position  and  left  free,  it  should  gradually  sink  to  the  ground.  If  i+.  drops 
abruptly  it  is  too  loose ;  if  it  does  not  sink  it  is  too  tight. 

When  taking  an  instrument  from  its  box,  it  is  not  immaterial  where  and  how  to 
take  hold  of  it.  To  lift  it  by  the  telescope,  circles,  standards,  or  wyes  is  improper, 
and  while  it  may  not  be  attended  at  once  with  any  senous  consequences,  yet  it  may 
sometimes  lead  to  some  permanent  injury,  and  it  certainly  is  always  iraught  with 
danger  to  the  permanency  of  the  adjustments.  In  handling,  it  is  always  best  to 
place  the  hand  beneath  the  leveling  base. 

When  mounting  an  instrument  on  the  screw  of  its  tripod,  or  screwing  any  of  its 
parts  together,  it  is  important  to  turn  the  part  in  the  direction  of  unscrewing  until  it 
is  perceived  by  a  slight  jar  that  the  threads  have  come  to  the  point  where  they  en- 
ter; the  motion  may  then  be  reversed,  and  the  parts  screwed  together. 

To  secure  an  even  wear  of  tangent  and  micrometer  screws,  they  should  be  uae4 
equally  on  all  portions  of  their  lengths. 


18 

Carrying  an  instrument  in  cold  weather  into  a  warm  room,  without  the  pro- 
tection of  its  box  or  bag,  will  cause  a  sudden  exchange  of  air  within  the  hollow 
spaces,  and  carry  with  it  dust  and  other  substances  through  the  minutest  openings. 
The  vapor,  also,  that  will  thus  condense  on  the  metal  surfaces,  if  it  were  not  pro- 
tected, will  have  a  tendency  to  settle  a  film  on  exposed  graduations,  making  them 
indistinct  and  difficult  to  read. 

Failure  to  protect  the  lenses  of  the  eye-piece  and  object-glass  of  a  telescope, 
when  not  in  actual  use,  from  the  effects  of  moisture,  dust,  etc.,  by  the  covers  pro- 
vided for  them  (eyepiece-lid  and  cap)  will  result  in  a  more  frequent  settling  of  a 
thin  film,  which,  like  the  fatty  substance  left  by  the  touch  of  the  fingers,  greatly 
impairs  the  Clearness  of  vision.  That  the  too  frequent  cleaning  of  the  lenses  must 
in  the  course  of  time  be  detrimental  to  their  brilliant  polish,  and  lead  to  a  corres- 
ponding loss  of  transparency  so  essential  to  the  proper  working  of  t  ^ood  telescope, 
is  apparent.  Too  much  care  cannot  be  taken  to  guard  the  lenses,  and  particularly 
the  inner  surfaces  of  the  lenses  comprising  the  objective,  against  any  film  that  may 
settle  on  them.  The  ill  effects  of  such  a  film  are  especially  noticeable  in  high-pow- 
ered telescopes  of  first-class  geodetic  and  astronomical  instruments.  In  short,  it 
should  be  remembered  that  the  slightest  film,  scratch,  or  dirt  will,  according  to  their 
nature  and  location,  impair  the  sight  through  a  telescope,  and  often  render  it  unfit 
for  accurate  work. 

The  glass  covers  protecting  the  compass,  arc,  and  verniers  from  exposure  need 
very  careful  brushing  and  cleaning,  the  same  as  the  lenses,  as  any  scratch  or  film 
will  impair  their  transparency.  If  at  any  time  the  ground-glass  shades  should  lose 
their  pure  whiteness,  by  either  dirt  or  film,  and  will  not  act  as  illuminators  of  the 
verniers  and  graduation,  take  them  out  of  their  frames  and  simply  wash  them  with 
soap  and  water. 

To  prevent  loss  of  magnetism  in  the  needle  of  instruments  provided  with  a  com- 
pass :  when  storing  away,  allow  the  needle  to  assume  magnetic  North  and  South ; 
then,  by  means  of  the  lifter,  raise  it  from  the  center-point  against  the  glass  cover. 

If  an  instrument  has  met  with  a  fall,  bending  centers  and  plates,  etc.,  it  should 
not  be  revolved  any  more,  in  order  to  preserve  the  graduations  from  still  further 
injury,  but  recourse  should  be  had  at  once  to  the  nearest  competent  maker. 

If  the  box  or  tripod  should  have  become  wet,  they  should  be  rubbed  dry,  and 
the  varnish  should  be  renewed  whenever  found  wanting. 

Loose  or  detached  resting-blocks  in  the  instrument-box,  or  any  looseness  of  the 
instrument  in  them,  are  very  detrimental  to  the  instrument  and  its  adjustments. 
Cracks  in  the  instrument-box,  the  absence  of  rubber  cushions  under  it,  worn-out 
straps  and  defective  buckles,  hinges,  locks,  and  hooks,  should  never  be  tolerated, 
as  the  remedy  is  so  easily  applied  by  any  mechanic.  Such  defects  and  imperfections 
are  known  to  lead  to  injury  of  the  instrument. 

The  place  where  instruments  are  kept  or  stored  away  should  be  thoroughly  dry 
and  free  from  gases.  The  placing  of  fused  chloride  of  calcium,  or  caustic  lirne,  in 
an  open  vessel  in  the  instrument-box  is  to  be  recommended  where  there  is  damp- 
ness ;  and  if  the  presence  of  sulphureted  hydrogen  is  suspected,  then,  cotton  satu- 
rated with  vinegar  of  lead,  placed  in  the  box,  will  prove  a  preventive  against  the 
tarnishing  of  solid  silver  graduations. 


Transportation  of  Instruments. 

DURING  the  progress  of  field  work  the  more  ordinary  and  portable  transits  and 
levelling  instruments,  etc.,  can  generally  be  carried  on  their  tripods  for  ease  and 
dispatch.  Nothing  in  the  way  of  precise  instructions,  however,  as  to  the  best  me- 
thod of  carrying  an  instrument  :  whether  on  the  tripod,  in  the  arm  without  the 
tripod  —  placing  the  hand  beneath  the  leveling  base  —  or  in  the  box,  can  be  sug- 
gested here.  The  nature  of  the  ground,  the  surroundings,  the  size  and  weight,  and 
the  distance  to  be  traveled  over,  and  last  but  not  least  the  fineness  of  the  instru- 
ment, will  dictate  to  the  engineer  the  best  means  of  conveying  it  from  point  to  point 
in  order  to  protect  it  from  injury,  and  its  adjustments  from  derangement. 


19 

The  finer  and  finest  classes  of  field  instruments,  such  as  those  provided  with 
micrometer-microscopes,  should  always  be  placed  in  their  boxes  for  safe  conveyance 
—  no  matter  how  short  the  distance  —  for  fear  of  improper  handling,  and  because  of 
danger  of  unequal  expansion,  temporary  as  it  may  be,  of  such  parts  as  would  come 
in  contact  with  the  body  or  fingers. 

Carrying  an  instrument  on  its  tripod  without  slightly;  clamping1  its  prin- 
cipal motions,  will  wear  out  the  centers.    When  carrying  on  its  tripod, 
Plflmn  tftlA^PonP  J  in  TRANSIT»  when  placed  on  a  line  with  its  centers; 

e°Pe  }  in  LEVEL,  when  hanging  down. 

When  carrying  an  instrument  in  the  box  it  is  important  that  it  be  placed  therein 
exactly  in  the  position  and  manner  designated  by  the  maker.  Therefore,  upon  re- 
ceiving a  new  instrument,  the  first  step  should  be  to  study  its  mode  of  packing,  and 
if  necessary  a  memorandum  should  be  made  for  future  guidance  and  pasted  in  the 
box.  This  will  save  time  and  vexation,  as  some  of  the  boxes  for  field  instruments 
must  necessarily  be  crowded  to  be  light  and  portable. 

Before  placing  an  instrument  with  four  leveling  screws  in  its  box,  the  foot-plate 
should  be  made  parallel  to  the  instrument  proper,  and  then  brought  to  a  firm 
bearing  by  the  leveling  screws.  The  instrument  must  also  be  well  screwed  to  the 
slide-board,  if  one  is  provided,  as  is  the  case  in  most  of  our  transits.  Having  put 
the  instrument  in  the  box  in  such  a  position,  that  no  part  of  it  will  touch  the  sides, 
the  principal  motions  are  now  to  be  checked  by  the  clamp  screws,  to  prevent  mo- 
tion and  striking  against  the  box.  Wii,a  instruments  not  standing  erect  in  their 
boxes,  but  which  are  laid  on  their  sides  in  resting-places,  padded  with  cloth,  speci- 
ally provided  for  that  purpose,  their  principal  motions  must  not  be  clamped  until 
the  instrument  has  been  secured  in  a  complete  state  of  repose  in  these  receptacles, 
so  as  to  be  entirely  free  from  any  strain.  Care  must  be  taken,  too,  that  all  of  the 
detached  parts  of  an  instrument,  as  well  as  its  accessories,  are  properly  secured 
to  their  receptacles  before  shutting  the  box. 

When  shipping  an  instrument  over  a  long  distance  it  is  commendable  to  fill  the 
hollow  space  between  it  and  its  box  with  small  soft  cushions  made  of  paper,  or  of 
excelsior  or  shavings  wrapped  in  soft  paper,  taking  care  not  to  scratch  the  metal 
surfaces,  nor  to  bend  exposed  parts,  nor  to  press  against  any  adjusting  screws. 

For  greater  safety  in  transportation  by  express,  the  instrument-box  itself  should 
always  be  packed  in  a  pine- wood  box  one  inch  larger  all  around.  For  the  ordinary 
size  of  field  instrument  the  packing-case  should  be  provided  with  a  strong  rope 
handle,  which,  like  the  strap  of  the  instrument  box,  should  pass  over  the  top  of  the 
case  and  through  holes  in  the  sides,  the  knots  being  within  the  case  and  strongly 
secured.  In  cases  where  the  gross  weight  of  the  entire  package,  as  prepared  for 
shipment  in  the  above  manner,  exceeds  40  or  50  Ibs.,  then  two  men  should  handle  it, 
and  two  strong  rope  handles,  one  at  each  end  of  the  packing-case,  should  be  provi* 
ded.  In  order  to  check  jars  and  vibrations  while  en  route,  the  loose  space  between 
the  instrument-box  and  the  packing-case  is  to  be  filled  with  dry  and  loose  shavings. 

The  cover  bearing  the  directions  should  always  be  screwed  on  and  marked  in  large 
black  letters.  Example: 

THIS  SIDE  UP. 

HANDLE    WITH   GREAT 

Scientific  Instrument. 

Mr.  George  Brown, 

36   West  Street, 

Value  $                                            Cleveland \ 
_^ Ohio. 

From  JOHN  SMITH,  Chicago]  Illinois. 


,20 

The  upper  halves  of  the  four  sides  also  should  have  *CARE'  and   'KEEP 

DRY  '  marked  in  large  letters  on  them.  These  precautions  are  indispensable  for 
safe  conveyance  while  in  the  hands  of  inexperienced  persons,  as  without  them  mes- 
sengers will  often  carry  them  wrong  side  up. 

The  tripod  needs  packing  simply  in  a  close-fitting  box.  If  not  placed  in  a  box, 
it  often  happens  that  legs  or  shoes  are  broken  off  while  en  route,  or  that  the  tripod 
bead  becomes  bent. 

Many  hundreds  of  instruments,  packed  as  explained  above,  have  been  shipped 
by  us,  travelling  over  thousands  of  miles,  over  rough  roads,  on  stages  and  on  horse- 
back; and  the  instances  are  so  rare  where  one  has  become  injured  (and  then  only 
through  gross  carelessness),  that  this  mode  of  packing  must  be  regarded  as  the 
only  proper  one  for  conveying  instruments  of  precision  by  express  or  other  public 
carriers. 

Arriving  at  its  destination,  an  instrument  should  not  remain  packed  up  with 
cushions,  etc.,  any  longer  than  absolutely  necessary.  The  atmosphere  in  such 
boxes  naturally  must  be  close  and  often  moist,  and  consequently  has  a  tendency  to 
produce  the  ill  effects  by  moisture  mentioned  in  preceding  paragraphs. 


Some  Remarks  Concerning  Instrument  Adjustments. 

The  mechanical  and  optical  condition  of  instruments  used  in  geodesy,  and  their 
adjustments,  although  satisfactory  when  they  leave  the  maker's  hand,  are  liable  to  be- 
come disturbed  by  use.  It  is  therefore  of  vital  importance  that  the  person  using  an  in- 
strument should  be  perfectly  familiar  with  its  manipulations  and  adjustments.  He 
should  be  able  to  test  and  correct  the  adjustments  himself  at  any  time,  in  order  to  save 
trouble  and  expense,  as  well  as  to  possess  a  thorough  knowledge  of  the  condition  of  the 
instrument.  It  is  evident  that  if  the  character  of  an  instrument  is  not  properly  under- 
stood or  if  the  adjustments  are  considerably  out,  the  benefit  due  to  superior  design  and 
workmanship  may  be  entirely  lost.  Under  these  circumstances  an  instrument  may 
be  little  better  than  one  of  lower  grade. 

In  the  best  types  of  modern  instruments  the  principal  parts  are  so  arranged  that 
they  can  be  adjusted  by  the  method  of  reversion.  This  method  exhibits  an  existing 
error  to  double  its  actual  amount,  and  renders  its  correction  easy  by  taking  one-half 
the  apparent  error.  Thus  errors  of  eccentricity  and  inaccuracy  in  the  graduations  are 
readily  eliminated  by  reading  opposite  verniers  and  reversing  the  vernier  plate  180°  on 
the  vertical  center  and  taking  the  mean  of  the  readings ,  and  by  repeating  the  measure- 
ment of  an  angle  by  changing  the  position  of  the  limb  so  that  the  measurement  will 
come  on  different  parts  of  the  graduation.  The  striding  levels  and  levels  mounted  on 
a  metal  base  are  readily  tested  by  reversing  their  position  end  for  end.  In  the 
transit  plate-levels  the  adjustment  is  assured  by  turning  the  vernier  plate  180°.  Errors 
of  the  line  of  collimation  are  detected  or  eliminated  by  reversing  the  telescope  over 
the  bearings,  or  through  the  standards,  as  the  case  may  be.  In  short,  an  instrument, 
the  important  parts  of  which  are  not  capable  of  reversing  in  one  way  or  another,  cannot 
be  examined  quickly  and  accurately. 

The  adjustments  of  an  instrument,  and  particularly  those  of  its  cross- wires,  should 
be  taken  up  successively  in  a  systematic  manner.  The  proper  way  is  to  select  a  place 
from  which  they  can  be  conducted  in  succession  without  moving  the  instrument,  as 
none  of  the  adjustments  should  be  completed  independently  of  the  others.  This  method 
is  followed  by  the  maker,  and  will  save  time  and  vexation.  Any  auxiliary  apparatus 
that  may  be  available,  such  as  collimators,  etc.,  will  be  of  great  service  and  expedite 
the  work.  One  of  the  most  important  considerations  in  making  adjustments  (when 
the  same  are  greatly  disturbed,  as  when  new  wires  are  to  be  inserted),  is  to  place  all 
the  respective  parts  in  an  approximate  adjustment  without  introducing  any  strain 
except  what  properly  belongs  to  the  action  of  the  adjusting  screws  themselves.  The 
more  natural  the  method,  and  the  less  internal  strain  introduced  in  bringing  these  ad- 
justable parts  into  position,  the  more  lasting  will  be  the  final  adjustments,  provided  the 
•ustrument  is  otherwise  in  good  condition. 

It  is  important  that  all  adjusting  screws  and  nuts  should  fit  truly  on  the  surfaces 
against  which  they  operate,  with  only  a  mere  film  of  tallow  between  them,  so  as 
to  insure  a  true  metallic  contact,  and  that  they  be  brought  to  a  firm  bearing,  yet  with 
out  excessive  strain.  Opposing  screws  and  nuts  should  always  work  somewhat  freely, 
so  that  one  can  feel  when  they  come  to  a  true  bearing.  A  moderate  pressure 


21 

applied  with  an  adjusting  pin  about  one  and  one  half  inches  long,  and  held  between 
the  thumb  and  forefinger,  will  then  make  a  perfect  contact.  For  instance,  after  the 
opposing  capstan-heade«  I  screws  of  the  cross-wire  reticule  have  come  to  a  bearing,  it  is 
only  necessary  to  give  them  each  a  slight  turn,  say  from  20°  to  30°  (with  the  usual  pitch 
of  these  screws)  in  order  to  insure  such  a  tightness  that  a  moderate  pressure  of  the 
finger  upon  these  screws,  or  an  accidental  gliding  of  the  hand  over  them,  cannot  change 
their  relative  position.  On  the  other  hand,  if  one  pair  of  these  opposing  screws  be 
fastened  tightly  during  the  tentative  process  of  adjustment,  there  will  be,  in  all  likeli- 
hood,  at  the  end,  an  excessive  strain  exerted  upon  the  pair  of  opposing  screws  at  right 
angles,  which  will  make  itself  felt  at  any  change  of  temperature,  or  whenever  any 
external  pressure  may  be  momentarily  applied  to  them.  Jt  is  but  natural  that  these 
continual  changes  in  the  resultant  pressure  must  affect  the  adjustments  in  a  like  man- 
ner.  To  obviate  such  changes  the  procedure  should  be  as  follows :  — 

Having  placed  approximately  in  position  the  principal  wire  of  an  instrument :  viz., 
in  a  transit,  the  vertical  wire  in  a  plane  perpendicular  to  the  horizontal  axis  of  revolu- 
tion, in  a  level,  the  horizontal  wire  in  a  plane  perpendicular  to  the  vertical  axis 
of  revolution,  the  other  wire  should  be  approximately  adjusted  for  collimation, 
with  the  capstan-headed  screws  only  moderately  tightened.  This  accomplished,  the 
capstan -headed  screws  of  each  pair  in  succession  should  be  unscrewed  about  one- 
quarter  turn,  and  again  screwed  tight  the  same  amount.  Now  if  the  two  pairs  of 
opposing  screws  have  exerted  no  undue  strain  upon  themselves,  the  telescope  tube,  or  the 
wire  reticule,  the  principal  wire  will  still  be  in  the  perpendicular  plane  ;  but  if  the  screws 
have  been  used  too  much  the  wire  will  have  slightly  moved  out  of  the  perpendicular 
plane.  Therefore  all  four  capstan-headed  screws  will  have  to  be  released  again,  say 
about  |  turn,  so  that  they  may  be  moved  simultaneously  until  the  principal  wire  is 
again  in  a  plane  perpendicular  to  the  axis  of  revolution,  and  then  each  pair  in  succes- 
sion must  be  again  tightened  an  equal  amount.  The  adjustment  of  the  wires  lor  colli- 
mation must  now  be  made  in  turn  —  the  less  important  wire  should  always  be  taken 
up  first  —  by  slightly  releasing  the  capstan-headed  screw  away1  from  which  the  wire 
must  be  moved,  and  tightening  the  opposite  screw  the  same  amount,  and  repeating 
this  process  until  the  adjustment  is  gradually  perfected.  If  during  this  operation  either 
or  both  of  these  wires  Lave  become  so  much  displaced  that  the  capstan-headed  screws 
have  to  be  moved  more  than  a  quarter  turn,  it  would  be  advisable  to  slightly  release  all 
four  of  them  again,  in  succession,  and  commence  anew. 

It  should  be  said  here,  that  the  force  applied  by  the  capstan-headed  screws 
cannot  break  or  affect  the  tightness  of  the  wires  in  any  case,  since  the  reticule,  as 
made  by  us,  although  very  light  in  weight,  is  of  a  very  stiff  form.  Too  great  pressure 
exerted  by  the  capstan-headed  screws  against  the  outer  tube  of  the  telescope  may, 
however,  change  die  form  of  the  main  tube,  thereby  affecting  the  true  fitting  of  the 
object-slide,  and  creating  friction  of  so  serious  a  nature  as  to  lead  to  the  fretting  of  the 
object  slide  mentioned  in  other  paragraphs. 

In  following  the  above-described  course,  the  cross-wire  reticule  occupies  a  position 
in  the  telescope  free  from  any  excessive  side  strain ;  the  result  of  which  is  found  in  the 
greater  permanency  of  these  adjustments ;  and  although  it  may  require  a  little  more  time 
for  an  inexperienced  person  to  make  the  adjustments  in  this  manner,  the  satisfaction 
derived  from  their  greater  permanency  will  more  than  recompense  for  the  extra  time 
spent  on  them.  The  adjustments  should  be  made  at  leisure,  and  should  not  be 
meddled  with,  unless  they  appear  to  be  permanently  deranged;  when,  ordinarily, 
the  adjustments  will  merely  require  a  very  slight  turn  of  the  capstan-headed  screws 
and  opposing  nuts  in  the  proper  direction.2  Unequal  exposure  of  the  instrument  to  the 
sun,  or  exposure  to  sudden  changes  of  temperature,  may  for  a  time  expand  some 
parts  more  than  others,  so  that  the  instrument  may  seem  to  be  slightly  out  of  ad- 
justment. In  such  a  case  it  would  be  better  to  stop  temporarily  and  cover  the 
instrument  with  a  bag  to  allow  the  temperature  to  become  equalized,  instead  of  at- 
tempting adjustments  that  would  need  to  be  repeated  when  the  instrument  is 
again  in  a  normal  condition.  The  use  of  metals  of  different  co-efficients  of  expansion 
in  the  construction  of  corresponding  parts  of  an  instrument  w?ll  naturally  lead  to  a 

1  We  refer  here  exclusively  to  the  more  common  instruments  of  American  manufacture,  where  the 
shoulders  of  the  capstan-headed  screws  bear  against  ihe  outer  tube  of  the  telescope,  and  where  the  adjusting 
threads  are  contained  in  the  wire  reticule.     In  other  designs  where,  as  in   most  instruments  of  Cont  nenta> 
Europe,  the  capstan-headed  screws  are  made  to  butt  ajrainst  the  wire  reticule,  the  capstan-headed  screws 
towards  which  the  wire  mu-t  be  moved,  must  first  be  loosened.     In  the   latter  case  this  action   is  identical 
with  that  of  opposing  nuts  used  for  the  adjustment  of  most  telescope  levels  on  American  instruments. 
2  See  page  58. 


22 

permanent  derangement  of  adjustment ;  such  also  will  be  the  case  when  the  temperature 
of  an  instrument  is  greatly  altered  after  the  adjustments  have  been  completed.  A 
similar  result  is  caused  if  the  bubble  of  a  spirit  level  should  not  lengthen  symmetrically 
from  the  center  of  its  graduated  scale  in  varying  temperatures.  These  imperfections, 
however,  seldom  occur  in  instruments  of  modern  make  (or  if  they  occur,  they  are  gener- 
ally caused  because  the  principal  constituents,  glass  and  metal,  are  substances  of 
widely  differing  co-efficients  of  expansion),  and  are  generally  so  slight  in  well  made 
instruments,  as  to  be  of  little  practical  value,  and  may  be  overcome  by  adjusting  the 
instrument  while  at  a  mean  temperature  of  an  entire  season. 

If  an  instrument  does  not  remain  in  adjustment  a  reasonable  length  of  time,  the  • 
cause  that  leads  to  the  trouble,  such  as  a  loose  object-glass  or  cell,  loose  object-slide, 
worn  out  screws  or  bearings,  etc.,  must  be  found  and  remedied.    If  this  is  beyond  the 
scope  of  the  operator  the  corrections  should  be  made  by  an  instrument  maker. 

Some  Facts  Worth  Knowing. 

The  Line  of  Collimation. 

The  expression  "Line  of  Collimation/'  usually  defined  vaguely  in  treatises  ou 
geodetic  instruments,  generally  means  any  line  of  sight  in  a  telescope  given  by  the  inter- 
section of  the  cross- wires,  whether  they  are  in  perfect  adjustment  or  not.  The  term 
*  Line  of  Collimation,"  should,  however,  be  confined  solely  to  the  line  of  sight  defined 
by  the  cross-wires  when  they  are  in  perfect  adjustment,  with  reference  to  the  optical; 
axis  of  the  object  glass ;  and  any  difference  existing  between  the  optical  axis  of  an  ob- 
ject glass  and  the  actual  line  of  sight  as  delineated  by  the  geometrical  axis  of  the  instru- 
ment is  the  "  Error  of  Collimation." 

The  principal  optical  axis  of  an  object-glass  is  the  line  passing  through  the  optical 
centers  formed  by  the  curvatures  and  the  thickness  of  the  two  lenses  composing  it. 
Thus  it  will  be  seen  that  it  is  a  well  defined  axis,  giving  direction  to  the  light  passing 
through  an  object  glass,  and  that,  when  the  intersection  of  the  cross-wires  is  placed  in 
its  prolongation  at  the  focus  of  the  object  glass,  it  becomes  the  axial  or  fundamental 
line  by  and  from  which  all  measurements  by  telescopic  sighting  are  made.  It  is  the  line 
of  collimation. 

To  make  a  good  instrument,  therefore,  it  is  necessary  that  the  outer  circumference 
of  the  lenses  composing  an  object  glass  shall  be  truly  concentric  with  the  optical  cen- 
ters. The  aim  of  the  maker  is  to  so  construct  his  instruments  that  this  optical  axis 
shall  be  truly  concentric  with  the  geometrical  axis  of  the  telescope  and  that  the  latter 
shall  also  occupy  a  normal  position  with  regard  to  the  geometrical  axis  of  all  other  im- 
portant parts :  upon  this  depends  the  proper  working  of  an  instrument. 

In  the  larger  geodetic  and  stationary  astronomical  instruments,  the  telescopes  of 
which  are  arranged  only  for  distant  sighting,  this  condition  is  readily  obtained  ;  but  it 
becomes  very  difficult  of  attainment  hi  the  smaller  geodetic  instruments,  since,  owing  to 
the  varying  position  of  the  focussing  slide  when  set  for  different  distances,  the  optical 
axis  may  not  always  remain  truly  coincident  with  the  geometrical  axis  of  the  telescope. 
Hence  in  these  instruments,  carefully  adjusted  for  distant  sights,  there  is  frequently  an 
error  of  collimation  when  nearer  sights  are  taken.  In  the  latter  case  the  intersection 
of  the  cross-wires  remains  no  longer  exactly  in  the  optical  axis,  its  displacement 
being  the  cause  of  the  error  observed  —  disregarding  momentarily  the  other  and  more 
complicated  features  of  different  instruments,  upon  which  the  line  of  collimation  also 
depends. 

In  the  Engineer's  transit,  however,  the  line  of  collimation  must  also  lie  exactly 
at  right  angles  to  the  axis  of  revolution  of  the  telescope,  so  that  when  this  axis- 
is  placed  in  a  horizontal  position,  the  line  of  collimation  shall  describe  a  truly  vertical 
plane,  whether  the  telescope  be  mounted  in  the  centre  of  the  instrument  or  outside  of 
the  plates,  or  whether  it  be  focussed  for  long  or  short  sights.  In  the  more  common 
instruments  of  this  class,  where  the  telescope  is  situated  in  the  center  of  the  instru- 
ment, the  intersection  formed  by  the  line  of  collimation  and  the  horizontal  axis  of  revo- 
lution is  also  required  to  lie  truly  in  the  prolongation  of  the  vertical  axis  of  revolution, 
so  that  there  be  no  eccentricity  between  the  vertical  axis  of  revolution  and  the  line  of 
collimation  when  sights  are  taken  at  objects  nearer  than  200  feet. 

In  transits  of  this  latter  type,  and  in  which  the  above  conditions  are  fulfilled,  the 
Bights  taken  would  at  once  define  the  true  angle,  and  no  reversing  of  the  telescope 
would  be  necessary,  were  it  not  for  other  reasons.  On  account  of  the  necessity  for 
eliminating  the  eccentricity  and  error  of  graduation  and  verniers,  as  well  as  for  eliminat- 
ing errors  arising  from  an  inaccurate  adjustment  of  the  line  of  collimation  and  of  th& 


23 

adjustment  of  the  telescope  in  the  vertical  plane,  an  instrument  should  be  reversed  and 
an  angle  should  toe  repeated.  These  remarks  apply  equally  to  transits  made  with  the 
telescopes  in  an  eccentric  position.  If  the  line  of  collimation  is  truly  at  right  angles  to 
the  horizontal  axis  of  revolution,  the  amount  of  the  offset  from  the  line  through  the 
center  of  the  instrument  to  the  line  of  collimation  will  equal  the  eccentricity  of  the  latter, 
and  will  remain  the  same  whether  the  sights  be  long  or  short.  As  a  rule,  however,  the 
small  geodetic  instruments  of  the  latter  class  cannot  be  constructed  with  the  same  de- 
gree of  perfection  as  those  with  the  telescope  in  the  center :  and  in  consequence  the 
engineer  using  such  instruments  will  have  to  rely  upon  methods  of  observing  that  will 
eliminate  all  instrumental  errors. 

In  the  engineer's  wye  level  the  line  of  collimation  must  be  truly  concentric  with 
the  object-slide  and  outer  rings ;  and  it  is  also  necessary  that  the  telescope  be  well  bal- 
anced from  the  center  of  the  instrument,  in  order  to  project  a  truly  horizontal  line. 

Difficult  of  attainment  as  the  foregoing  conditions  may  seem,  it  is  proper  to  say 
that  improved  tools,  and  a  generally  better  understanding  of  the  principles  governing 
a  telescope  and  its  relation  to  the  instrument,  have  done  so  much  toward  the  perfec- 
tion of  geodetic  instruments,  that  while  it  may  not  always  be  possible  to  make  an 
instrument  in  which  the  line  of  sight  for  both  wires  remains  true  for  all  distances,  that 
result  can  generally  be  secured,  for  at  least  the  principal  wire,  without  requiring  any 
other  but  the  regular  cross-wire  adjustment. 

By  the  foregoing  explanation  it  will  be  readily  understood  that  it  is  of  great  im- 
portance to  have  the  focussing  slide  of  such  a  telescope  truly  fitted,  in  order  that  the 
optical  axis  of  the  object-glass  may  coincide  with  the  geometrical  axis  of  the  telescope, 
whether  this  slide  moves  in  the  main  tube  and  carries  the  object-glass,  as  is  the  custom 
now  in  the  smaller  instruments  ;  or  whether  it  moves  in  special  rings  provided  for  it  in 
the  main  tube  at  the  eye-end,  where  it  will  contain  the  eye-piece  and  the  cross-wires, 
as  is  the  case  in  all  larger  instruments.  Any  lateral  motion  in  the  focussing  slide  that 
carries  the  object-glass  or  the  cross-wires,  will,  therefore,  derange  the  adjustment  of  the 
line  of  collimation.  However,  it  is  equally  as  clear  that  a  wabbling  of  a  focussing  slide 
carrying  an  eye-piece  which  serves  only  the  purpose  of  a  compound  microscope  for 
close  observations  of  the  wires  and  the  image  of  an  object,  is  of  no  account  save  that 
such  lateral  motion  may  be  so  great  that  the  obliquity  which  the  optical  axis  of  the 
eye-piece  may  at  times  have  with  respect  to  the  optical  axis  of  the  telescope,  may  cause 
some  parallax,  if  the  wire  and  image  under  observation  are  not  sharply  focussed  to- 
gether. In  concluding,  it  may  not  be  considered  amiss  for  a  full  understanding  of  this 
subject,  to  also  mention  in  this  connection,  that  any  transparent  substance,  such  as 
prisms*  lenses,  or  Shade-glasses,  introduced  between  the  object  sighted  at  and  the 
object-glass,  will  deflect  the  line  of  sight  from  its  true  course,  unless  such  parts  can  be 
made  optically  and  mechanically  perfect,  which  is  rarely  the  case  without  elaborate 
adjusting  apparatus.  The  introduction  of  a  lens  or  lenses  between  the  object- 
glass  and  wires,  or  that  of  a  glass  micrometer,  will  also  have  the  tendency  to  deflect 
the  optical  axis  and  aftect  the  line  of  collimation,  not  to  speak  of  the  conse- 
quent loss  of  light  caused  thereby  and  film  forming  on  the  surfaces.  For  this 
reason,  "Porro's  telescope,"  which  requires  a  lens  between  the  object- 
glass  and  the  wires,  complicates  ihe  above  conditions  of  a  measuring  telescope  ;  and 
while  it  may  prove  of  some  value  in  stadia-work  —  to  enable  to  measure  from  the 
center  of  the  instrument  instead  of  from  a  point  in  front  of  the  object-glass  equal  to 
its  focal  length — this  feature  can  never  be  successfully  adapted  to  the  engineer's  transit 
as  long  as  the  proper  functions  of  the  transit  telescope,  as  explained  above, 
are  considered  of  the  greatest  importance.  The  successful  performance  of 
an  instrument  should  not  be  sacrificed  for  the  sake  of  some  doubtful  novelty. 

The  proper  way  of  attaching  prisms  and  colored  glasses  necessary  to  make  sun 
and  star  observations  is  to  put  them  upon  the  eye-piece  of  a  telescope.  After  the  rays 
from  an  object  have  passed  through  the  object-glass  and  the  plane  containing  the 
wires,  the  line  of  sight  as  fixed  by  the  object,  optical  axis,  and  the  wires,  cannot  be 
changed  by  additional  refraction.  The  best  way,  therefore,  is  to  apply  prisms  and 
shade-glasses  between  the  eye  and  the  lens  nearest  the  eye. 


Aluminum  for  Instruments  of  Precision. 

In  consequence  of  improvements  in  the  production  of  pure  aluminum  and  a  cor- 
responding great  reduction  in  its  cost,  we  frequently  receive  inquiries  as  to  the  adapt- 
ability of  this  metal  for  the  manufacture  of  engineers'  and  surveyors'  instruments. 

We  may  be  permitted  to  say,  that  while  we  are  among  the  earliest  advocates  of 
aluminum  and  its  alloys  for  mathematical  instruments  (see  Scientific  American, 
Feb.  1,  1868),  we  are  not  so  sanguine  concerning  its  adoption  for  every  class  of 

*  The  object  prism,  so  called,  attachable  to  the  object  end  of  a  mining  telescope  to  aid  in  steep  sighting, 
from  its  position  between  the  object  glass  and  the  object  sighted  at,  must  of  necessity  be  of  very  limited  use- 
fulness, since  the  slightest  change  of  the  prism  or  its  mounting  or  a  change  of  the  position  of  the  telescope 
itself  or  of  its  object  slide  will  almost  certainly  deflect  the  line  of  sight  from  its  true  course  and  give  no  satis- 
factory results. 


24 

geodetic  instruments,  as  these  inquiries  would  warrant  us  to  be.  There  are  certain 
advantages  derived  from  the  use  of  the  lighter  aluminum  instead  of  copper  and  its 
alloys,— the  metals  now  employed  for  field-instruments ;  but  the  disadvantages  are 
that  pure  aluminum,  although  very  rigid,  is  nevertheless  a  very  soft  metal  like  tin, 
and  that,  when  alloyed  with  10  per  cent,  copper,  to  make  it  harder,  it  becomes  very 
brittle,  but  when  alloyed  with  20  per  cent,  or  30  per  cent,  of  copper,  it  becomes  so 
brittle  as  to  break  like  glass,  therefore,  it  can  be  used  only  with  great  caution  as  a 
material  for  precise  instruments. 

An  alloy  of  95  parts  aluminum  and  5  parts  of  silver  by-  weight  has  been  found  to 
give  good  results,  being  more  rigid  and  harder  than  the  pure  metal,  and  but  little 
heavier,  while  it  is  almost  as  resistent  to  corrosion,  polishes  well,  and  is  said  to 
be  better  for  graduation ;  but,  the  fact  that  it  contains  silver,  will,  of  necessity, 
limit  its  use  to  the  more  exceptional  class  of  work. 

Very  little  is  gained  in  the  way  of  reducing  the  weight  of  an  instrument  by  em- 
ploying aluminum  bronze  (90  per  cent,  copper  and  10  per  cent,  aluminum).  The 
parts  of  instruments  made  of  the  latter  metal  might  be  easily  reduced  somewhat 
in  thickness  on  account  of  its  greater  rigidity  as  compared  with  copper  alloys ;  yet 
to  lessen  the  tendency  to  vibration,  and  also  in  order  to  withstand  the  wear  and 
tear  of  the  field  use  of  an  instrument,  such  parts  need  a  little  more  mass,  or  dead 
weight  as  it  may  be  called.  It  is  then  found  that  the  weight  of  an  instrument  re- 
mains materially  the  same  as  ever.  An  exception  to  the  rule  may  exist  in  the  con- 
struction of  the  larger  and  stationary  astronomical  instruments,  where  aluminum 
bronze  may  be  used  to  a  certain  extent  to  advantage.  Its  adoption  is,  however, 
restricted  to  non-revolving  parts,  since,  when  closely  fitted  into  bearings  made  of 
the  softer  copper  and  tin  alloys,  the  friction  and  wear  of  these  parts  is  so  marked 
that  we  would  never  think  of  substituting  it  for  steel,  bell  metal  or  phospho** 
bronze,  or  for  any  work  requiring  a  smooth  and  accurate  motion. 

There  can  be  no  doubt  that  aluminum  possesses  great  utility  over  brass  in  the 
construction  of  instruments  of  minor  importance.  Sextants,  reflecting  circles,  and 
the  more  ordinary  compasses*  can  be  made  of  it  to  some  extent,  also  parts  of  transits, 
plane-tables  and  other  instruments,  etc.  We  are  using  it  very  extensively,  but  for 
reasons  already  stated  above,  we  are  not  prepared  to  advocate  its  general  adoption  for 
instruments  of  precision.  It  is  only  in  cases  where  a  judicious  use  of  this  metal  will 
be  a  necessity  for  the  successful  construction  of  an  instrument,  as  for  instance  in  our 
new  style  of  mining  transit,  permitting  of  vertical  sights  up  and  down  a  shaft  without 
the  use  of  an  extra  side  telescope,  where  certain  detachable  parts  of  the  instruments 
are  mounted  in  an  excentric  position,  and  unless  such  parts  are  made  of  aluminum 
they  would  require  a  heavy  counterpoise. 

It  is  principally  the  indiscriminate  use  of  aluminum  that  we  would  warn  against.  To 
make  this  fully  understood,  it  will  be  necessary  to  explain  that  all  the  finer  bearings 
of  an  instrument  made  of  aluminum,  such  as  centers,  object  slides,  leveling  and  micro- 
meter screws,  etc.,  will  have  to  be  bushed  with  a  harder  and  non-friction  metal,  to  guard 
against  friction  and  wear  and  to  obtain  the  close  fitting  of  such  parts,  and  permanency 
of  adjustments  so  necessary  in  instruments  of  precision.  Now,  to  make  the  princi- 
pal  bearings  of  an  instrument  of  different  metals  has  the  tendency  to  weaken  the 
parts  so  treated,  to  make  them  less  secure,  and  to  render  the  adjustments  more 
liable  to  derangement  on  account  of  unequal  contraction  and  expansion  between 
the  two  metals.  It  simply  means,  then,  that  the  present  high  state  of  perfection 
in  geodetic  instruments,  which  retain  their  adjustment  in  the  varying  temperatures 
and  climes  of  our  zone,  shall  be  abandoned,  and  we  go  back  many  years  to  when 
the  indiscriminate  use  of  widely  different  metals  often  made  an  instrument  entirely 
unreliable,  except  when  used  in  the  temperature  in  which  it  was  adjusted. 

Modern  instrument-making  has,  however,  already  achieved  great  results  in  re- 
ducing the  weight  of  field  instruments.  By  improved  designs  and  by  the  use  of 
harder  metals  in  place  of  the  soft  brass,  remarkable  changes  have  been  brought 
about  in  the  weight  of  instruments.  They  are  no  longer  the  heavy  and  formless 
structures  of  soft  or  hammered  brass  as  of  yore,  but  are  of  the  type  and  character 
of  a  long-span  steel  bridge,  as  compared  with  an  old-fashioned  wooden  structure. 
Every  important  member  of  an  instrument  is  now  calculated  with  regard  to  its 
strength,  and  the  materials  aie  particularly  chosen  for  the  part  they  are  10  perform. 
•  Commercial  Aluminum,  unless  obtained  from  reliable  sources,  often  contains  a  small  amount  of  iron. 


25 

Owing  to  the  many  improvements  made  in  the  designs,  the  use  of  better  materials, 
the  application  of  specially  designed  tools  and  machinery,  it  is  no  longer  necessary  to 
use  large  and  heavy  instruments.  An  instrument  of  about  two-thirds  the  size  and 
weight  of  those  made  formerly  will  now  do  the  same  class  of  work.  It  is  by  these 
methods  that  lightness  has  been  gained,  and  to  them  we  must  look  for  advances  in  the 
future.  Unless  the  size  of  an.instrument  is  decreased,  the  resistance  of  its  exposed  sur- 
faces to  wind  pressure,  causing  sudden  vibrations  or  tremor  in  the  instrument,  will  of 
necessity  require  a  certain  amount  of  weight  to  secure  the  needed  steadiness,  and  if  this 
weight  is  not  in  the  instrument  proper,  it  will  have  to  be  in  its  tripod  legs.  This  is 
especially  true  in  this  era  of  high  telescope  powers  and  sensitive  spirit-levels.  What  is 
needed  is  that  engineers  and  surveyors  should  have  more  confidence  in  instruments  of 
smaller  size  as  made  by  the  best  makers. 

Wherever  less  weight  is  of  great  importance  our  patrons  should  not  hesitate  to  order 
our  smaller  Transits  Nos.  2,  3,  or  4,  weighing  10^  and  6  Ibs.  respectively,  in  preference 
to  a  larger  instrument  made  of  Aluminum  and  divided  to  single  minutes,  but  of  equal 
weight.  These  small  instruments  are  just  as  durable  and  capable  of  doing  just  as  close 
work  as  the  larger  ones.  Being  mad*  of  a  like  metal  throughout,  whose  coefficient  of 
expansion*  is  lower,  they  will  retain  their  adjustments  better  than  larger  ones  made  in 
whole  or  in  part  of  Aluminum.  —  Suppose  an  instrument  is  adjusted  in-doors  and  im- 
mediately is  taken  into  the  cold  atmosphere  of  winter :  other  things  being  equal,  if  the 
coefficient  of  expansion  of  some  parts  differ  the  adjustments  will  very  likely  be 
deranged.  —  Besides,  the  instrument  being  smaller,  the  boxes  are  likewise  smaller,  thus 
reducing  the  weight  and  making  it  more  portable  at  the  same  time.  The  same,  in  a 
measure,  can  be  said  of  the  tripod,  although  it  is  against  our  convictions  to  use  a  lighter 
tripod  with  a  small  transit  than  is  used  on  the  larger  ones. 

The  only  exception  to  the  above  exists  in  the  Telescope,  which,  of  course,  being 
correspondingly  shorter  in  a  small  instrument,  will  have  a  smaller  aperture  and  less 
power.  However,  to  secure  the  same  aperture  and  power  for  Transits  Nos.  2  and  3 
(No.  4  being  inverting),  as  for  our  Transit  No.  1,  with  an  erecting  eyepiece,  it  is  only 
necessary  to  order  an  inverting  telescope  to  attain  these  conditions. 

In  conclusion  we  wish  to  say  that  the  future  developments  in  alloying  it  as  a  base 
with  other  metals,  or  combination  of  metals,  will  be  watched  by  us  with  due  care,  and 
that  whenever  such  developments  warrant  their  adoption  for  instruments,  as  already 
exemplified  in  many  new  types  of  instruments  enumerated  in  our  catalog,  made  in  part 
or  almost  wholly  of  such  alloys,  we  are  glad  to  do  so. 

*  The  Ideal  metal  for  a  Survey ing  Instrument  is  that  -which  has  a  coefficient  of  expansion  equal  to  that  of 
its  glass  part* i  so  as  to  retain  the  adjustments  in  varying  temperatures. 

Coefficient  of  glass  per  linear  foot,  for  i°  F 0.000054  inches. 

"    steel  0.000076 

"  "    brass       "  "".......        0.000125 

"  •*   aluminum  per  linear  foot,  for  i°  F 0.000148      " 

Aluminum  is  farthest  removed  from  the  above  requirements,  steel  or  cast  iron  being  nearest,  and  also 
fighter  and  harder  than  brass ;  and  non-friction  metals  would  be  more  generally  adopted  were  it  not  for  the  usa 
of  the  compass  and  the  liability  to  rust  in  the  field. 


Repair  of  Instruments. 

We  are  often  applied  to  for  correcting  new  and  repairing  old  instruments  made  by  other 
makers.  We  will  here  remark,  that  as  workmanship,  material  and  construction  of  different 
makers'  instruments  vary  from  one  another,  it  is  oftentimes  impossible  to  repair  them  in  an  en- 
tirely  satisfactory  manner  without  going  into  an  unwarrantably  great  expense,  or  without  mak. 
ing  such  alterations  as  would  practically  make  a  new  one.  We  will  always  guarantee  in  such 
cases  to  put  the  instrument  in  as  good  order  and  adjustment  as  the  character  of  its  construction, 
workmanship  and  material,  the  extent  of  damage  and  the  general  wear  will  permit,  and  that  all 
repairs  are  promptly  and  conscientiously  made.  The  charges  will  be  according  to  lime  con- 
sumed, and  as  low  as  is  consistent  with  good  work.  Parties  sending  instruments  should  point 
out  in  detail  whatever  parts  they  wish  to  have  repaired ;  but  the  best  course  to  be  pursued  is  to 
have  the  instrument  put  in  thorough  order  and  adjustment,  implying,  as  it  does,  that  the  firm 
should  make  such  warrantable  repairs  as  will  make  it  as  serviceable  as  possible.  This  course  is 
always  more  expensive,  but  the  most  satisfactory  to  insure  good  work,  and  it  is  alsothe  cheapest  in 
the  e'nd.  —  Ourown  ins'rumen-s,  whenever  practicable,  should  always  be  sent  to  us  for  repairs  to 
insure  fullest  satisfaction.  Much  time  j  nd  money  H  frequently  saved  by  so  doin-jr,  as  we  are  in  a 
position  to  duplicite  parts  from  stock  on  hand,  fn  sending  an  instrument  to  us  from  a  distance  it 
should  he  carefully  placed  in  its  box  and  then  again  in  a  packing  box,  as  explained  under  "  Trans- 
porta'ion  of  Instruments,"  Part  I.,  in  order  to  conform  to  the  rules  of  most  of  the  large  Express 
Companies,  which  will  admit  it  to  single  rates. 


26 


Cross-section  of  spirit  levels  as  used  for  instruments  of  precision  (see 
pages  7  and  38),  interior  surface  showing  the  barrel  form  with  curvature  ground  to 
certain  value  of  arc,  diameter  of  arc  depending  on  the  degree  of  sensitiveness  required. 


Cross-section  of  spirit  levels  as  above,  but  provided  with  an  air-chamber 
for  adjusting  length  of  the  bubble  for  different  temperatures  as  used  in  the  leveling 
instruments  of  precision  and  for  astronomical  work. 


vision 

TABLE 

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50     100      150     200      300     400    500    1000 

,  *  -s 

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Sec. 

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I  /  IO 

344 

8 

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•°39 

I/IO 

215 

3/20 

322 

10 

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.049 

I/IO 

172 

3/20 

258  ; 

12 

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2mm 

54 

27 


Engineers9 
Instruments   and  Their   Adjustments. 


General  Remarks. 

THE  OPTICAL  PART. 

In  the  construction  of  telescopes  for  engineers'  instruments,  several  difficulties 
present  themselves.  To  be  portable,  the  telescope  must  be  of  small  aperture,  and 
of  short  focus.  To  make  it  of  short  focus  and  yet  retain  sufficient  aperture  to  give 
the  light  necessary  with  the  eye-pieces  used,  requires  especial  care  on  the  part  of 
the  maker,  both  in  securing  the  true  curves  for  the  crown  and  flint  glass  lenses, 
which  make  up  the  achromatic  object-glass,  and  in  adapting  an  eye-piece  which 
will  secure  a  flat  field,  with  the  least  distortion. 

After  careful  experiments  with  the  formulas  suggested  by  the  distinguished  astron- 
omer, Sir  George  B.  Airy,  and  the  late  Mr.  Kellner,  of  Wetzlar,  (the  two  best  formulas 
known),  we  have  adopted  the  latter.  Mr.  Kellner's  formula  employs  four  lenses, 
mounted  separately,  and  so  arranged  as  to  secure  a  flat  field  of  the  sharpest  definition, 
to  the  very  edge. 

The  magnifying  power  of  the  telescope  depends  upon  the  relation  between  the 
focal  length  of  the  object-glass  and  the  focal  length  of  the  eye-piece,  considered  as 
a  single  lens :  Thus— 

If  F  =  focal  length  of  the  object-glass, 

f  =     kk        **        "    eye-piece, 

TGI 

Then  -j-  =  magnifying  power  of  telescope. 

It  is  readily  seen  that  the  magnifying  power  may  be  increased  or  diminished  by 
altering  the  focal  length  f ,  of  the  eye-piece ;  but  if  the  maker  increases  the  power 
too  much,  since  only  a  fixed  amount  of  light  can  enter  the  object-glass,  this  fixed 
amount  of  light  is  spread  over  too  much  surface  in  the  field  of  view,  and  the  object 
seen  is  therefore  too  faint.  If  the  maker  gets  the  magnifying  power  too  small, 
then  the  engineer  has  a  difficulty  in  pointing  the  telescope  accurately.  Some  other 
points  in  regard  to  the  magnifying  power  will  be  referred  to  in  the  description  of 
the  transit  telescope.  We  have  found  about  twenty-four  diameters  to  be  the  most  satis- 
factory power  for  our  Engineers'  Transit  Telescope  ;  and  for  levels  the  powers  in- 
crease in  proportion  to  the  size  of  the  instruments. 

Very  much  depends  upon  the  optical  part  of  any  instrument,  and  very  little  has 
been  put  into  the  hands  of  the  practical  engineer  by  which  he  may  rigidly  test  it. 
f.C|ie  following  suggestions  may  be  found  convenient. 

The  telescope  should  come  sharply  into  focus,  and  a  very  little  movement  of  the 
focussing  screw,  either  way,  should  cause  the  image  to  blur.  When  it  is  sharply 
focussed,  covering  any  part  of  the  object-glass  without  altering  the  focus,  should 
not  alter  the  sharpness  of  definition  but  merely  cut  off  light.  The  pencil  of  light 
which  enters  the  object-glass,  should  come  out  at  the  eye  end.  To  ascertain  this, 
gee  whether  a  pointer  which  you  place  just  in  contact  with  the  edge  of  the  object- 
glass,  can  be  wholly  seen  in  the  small  disc  of  light  which  you  will  notice  at  the 
small  opening  of  the  eye  end  when  you  draw  your  head  back  some  inches  from  the 
telescope,  and  point  the  telescope  towards  the  sky.  If  the  pointer  cannot  be  seen 
up  to  the  very  edge,  then  the  maker  has  inserted  a  diaphragm  which  cuts  off  light 
from  the  object-glass,  and,  very  probably,  to  conceal  the  faults  in  making.  In  tnifc 


28 

case  the  real  aperture  of  the  telescope  is  found  by  moving  the  pointer  over  the  object- 
glass  until  its  point  is  just  visible,  and  measuring  from  the  inner  edge  of  the  brasi 
cell  holding  the  object-glass  to  the  pointer.  Twice  this  distance  subtracted  from 
the  distance  between  the  two  edges  of  the  brass  cell,  will  give  the  real  or  clear 
aperture  of  the  telescope.  The  clear  aperture,  divided  by  the  diameter  of  the  small 
circle  of  light  at  the  eye  end,  when  the  telescope  is  focussed  on  a  distant  object, 
will  give  the  magnifying  power  of  the  telescope.  Thus  the  clear  aperture  of  a  tele- 
scope, measured  by  means  of  a  pair  of  dividers  and  a  scale,  was  1™-  35,  while  the 
diameter  of  the  circle  of  light  at  the  eye  end,  was,  0'°-  06.  In  this  case,  the  magnify- 
ing power  of  the  telescope  was  -jr-  =  22.5  diameters. 

Another  way  to  determine  the  magnifying  power,  is  to  measure  the  angular 
distance  between  two  points  with  a  transit,  and  then  measure  the  same  distance 
with  the  telescope  of  which  the  power  is  to  be  ascertained,  placed  so  that  the  tran- 
sit must  point  into  its  object-glass  and  see  the  same  angular  distance  through  the 
second  telescope  inverted.  Then  calling  the  first  angle  A,  and  the  angle  as  seen 
diminished  through  the  introduction  of  the  second  telescope  inverted  a,  we  have 

the  magnifying  power  of  the  second  telescope  =  -  an"  (•?  .  Thus  the  angle  sub- 
tended by  a  window  sash,  several  hundred  feet  away,  was  measured  by  a  transit 
instrument  direct,  and  found  to  be,  1°58'  50".  When  a  Y  level,  previously  focussed 
on  a  distant  object,  w°s  set  before  the  transit,  with  its  object-glass  towards  th<j 
transit,  the  same  sash  \vas  measured  and  the  angle  was  found  to  be  but  3' 30".  In 
this  case,  therefore, 

/1°5S'50"\ 

tan.  I ^ 1     tan  0°59'25" 

the  magnifying  power  of  Y  level = )r&)"\          tan.V  r45"=34'°  diameters-- 

tan.  (     2    ) 

Or,  for  an  approximation,  a  card  cut  one  inch  wide  may  be  set  up  across  a  room 
by  the  side  of  a  measure  graduated  to  inches.  Then,  the  number  of  inches  on  the 
measure  seen  by  one  eye,  covered  by  the  image  of  the  white  card  seen  through  the) 
telescope  by  the  other  ^ye,  will  give,  roughly,  the  magnifying  power. 

It  is  dinicult,  without  months  of  use,  i;o  fully  test  an  instrument  in  all  its  parts ; 
but  in  choosing  an  instrument  the  engineer  should  bear  in  mind  that  the  making  of 
the  transit  ana  the  level  are  considered  to  be  feats  of  mechanical  skill.  It  should 
be  remembered  that  there  is  no  machine  so  delicate  that  it  can  finish  the  essential 
parts  of  an  instrument*  The  last  stages  in  its  making  must  depend  upon  the  personal 
skill  of  some  mechanic,  who  has  a  reputation  for  that  particular  work;  and  we  ar«i 
sorry  to  add,  that  so  difficult  is  it  to  secure  the  mechanical  skill  and  patience  re- 
quired  in  the  finishing  of  the  interior  pails,  the  only  essential  ones,  and  so  easy  is 
it  to  add  the  lacquer  and  polish  of  the  outside,  that  the  market  is  full  of  instruments 
sold  at  a  price  enough  lower  than  the  best  makers  can  work,  to  seem  to  effect  a 
large  saving  of  the  first  cost;  but  such  a  saving  is  money  borrowed  at  the  highest 
rate  of  interest,  when  the  cost  of  annual  repairs  is  considered.  It  is  better  at  the 
outset  to  buy  of  a  maker  who  is  noted  for  the  conscientious  accuracy  of  his  work. 
An  imperfect  rnck  motion ;  a  screw  turned  home  on  the  wrong  threa'd ;  a  wabbling 
of  the  object-slide  or  eye-piece;  a  slight  space  between  the  edge  of  the  vernier  ana 
the  limb  of  the  c.'rcle ;  in  fact,  any  mechanical  defect,  no  matter  how  slight  it  may 
seem,  may  be  taken  as  a  pretty  sure  indication  that  the  work  has  been  slighted  in 
other  parts  as  well,  and  should  have  a  strong  influence  in  guiding  the  selection  of 
an  instrument,  in  the  absence  of  a  test  by  work  i«  the  field. 


THE  ENGINEER'S  TRANSIT. 

In  the  first  part  of  this  catalogue,  the  peculiarities  and  improvements  in  this  in- 
strument have  been  pointed  out.  In  speaking  of  the  adjustments  of  these  instruments 
it  is  well  for  the  engineer  to  remember  that  the  construction  is  aimed  to  be  such  that 
\i  the  telescope  and  levels  are  carefully  adjusted  they  may  remain  so  for  even  a  number 
of  years  to  come,  if  the  instrument  suffers  no  rough  usage. 


ITrfpodfead 

2  //    Bolt 

3  //       >/  Mf 

J    „     //  Washer 

5  «    Leg 

6  Footplate 

7  Ba'/ and  Socket -Joint 

8  Le/efing  Head 

9  a      <Scretty 

10    //      JcretrCt/ps. 
/I  Shifting  P/ate 
12  Plumb  Bob suspending  cup 
IS    *     H  Chain  and  Hook 

14  Repeating  Center 

15  Clamp  Collar 
IGLoverClamp 


51  StdeL/irt  Rocker 

52  ,»    tfal 

53  Te/f  scope  /ix/s 

54  /        Barret 

55  E"ye  P/ecertountina 

56  Sp/ra/GrwreJcre/r 

57  Terrestrial  Eye  Piece 
56  Et/eP/'eceCap 

59  i     *  Ring 

60  M'/vRet/cu/e 
6/     a 


64  a     ff  jcretr 

65  „     ,i  jadd/e 


Thumbscrew 
Tangent&rev 


17  ,r 

18  » 

19  * 

20  f     ft  Piston,  Notshom 

21  n     t  Cap. Not  Shown 

22  Inner  center 

23  Horizontal  Circle 

24  VernierPlare  c/amp 

25  »« 

26  Vernier  Plate 

27  t       a  Tangent  Bracket 

28  f       ,i       *    iScrfft^  34 

29  »       a       »    Spring 

; 

30  TangentSpringPisto/i 

31  , 

32  Horizontal  Vernier 


34     *   Shade  from? 
*      ,  Glass 

36  Compass  corerG/ass 

37  Meed/e 

38  ,     P/wr 

39  „.    Liffer 

40  *      i, 


42 

43 
44 


66  it     it 

67  MjectM'de 

68  //     Head 

69  /,     Glass  cell 

70  /,     Glass 

'//     a    aide  Dusf  Guard 

72  <Si//7<Snade 

73  Telescope  Clamp 

«  „  <$crev 
75  *  //  Washer 
7$  n  7a/7gent<scn?>r 

77  Vertical  C/rc/e 

78  »        »  Guard 


\46     *       Jldjus  table  M/e  Bearing 

47  a      Cap  and<Screws 

48  <5ide  Level 

19    //    //  Jdjustingscrev 
50     t>    »  Fastening  jcreir 


Cross  Section  of  the  Berger  Transit. 

The  heavily  drawn  center  line  and  the  two  parallel  lines  drawn  at  right  angles  to 
it  in  the  above  cut,  indicate  conditions  required  in  a  perfectly  adjusted  transit. 


30 


31 

Description  of  the  Telescope. 

THE  object-glass  is  achromatic,  being  made  of  two  lenses,  one  of  crown  and  one 
of  flint  glass.  Both  these  lenses  are  made  of  the  celebrated  "Jena"  glass  (intro- 
duced about  1885),  which  has  a  greater  index  of  refraction  and  power  of  dispersion 
than  known  before  this  time.  For  the  most  part,  that  is,  whenever  the  diameter  of 
these  lenses  is  not  too  large,  we  —  since  1889  —  cement  them  together  so  as  to 
make  one  lens  only.  In  so  doing  the  disturbing  reflections  from  their  inner  sur- 
faces, and  the  settling  of  a  film  between  them  is  prevented,  besides  securing  to  the 
telescope  an  additional  amount  of  light  equal  to  about  8  per  cent.  The  curvatures 
are  computed  from  special  formulae,  so  that  the  telescope  may  have  the  largest 
aperture  possible  with  a  short  focal  length. 

The  engineer  will  appreciate  the  slightest  gain  in  the  diameter  of  the  object- 
glass,  since  the  amount  of  light  received  from  any  object  varies  as  the  square  of 
that  diameter.  Thus  an  object-glass  1£  inches  in  diameter  will  admit  half  as  much 
light  again  as  an  object-glass  one  inch  in  diameter. 

The  eye-piece,  or  ocular,  as  it  is  sometimes  called,  is  the  combination  of  lenses 
used  in  the  telescope  with  which  the  image  formed  at  the  focus  of  the  object-glass 
is  viewed. 

The  simplest  and  most  commonly  used  eye-piece  in  the  telescopes  of  instru- 
ments of  -precision,  where  spider-threads  and  micrometers  are  used  in  making 
measurements,  is  the  Eamsden  astronomical  or  positive  eye-piece.  It  consists  of 
two  plano-convex  lenses,  commonly  of  the  same  focus,  placed  apart  at  a  distance  of 
two-thirds  the  focal  length  of  either,  the  convex  sides  facing  each  other.  It  has 
the  advantage  of  being  placed  behind  the  focus  of  the  object-glass.  It  is  almost 
free  from  spherical  aberration,  and  gives  a  perfectly  flat  field  of  view,  so  that  the 
spider-threads  can  be  seen  distinctly  throughout  their  entire  length.  Unfortun- 
ately it  is  not  entirely  free  from  chromatic  aberration,  that  is,  not  strictly  achro- 
matic, and  therefore  the  Kellnerand  Steinheil  eye-pieces  are  frequently  preferred,  as 
in  them  the  chromatic  aberration  is  sensibly  eliminated,  so  that  a  bright  object 
viewed  with  a  normal  eye  will  appear  achromatic,  a  condition  as  important  in  the 
eye-piece  as  in  the  object-glass. 

The  Kellner  eye-piece,  also,  consists  of  two  lenses.  The  one  nearest  the  eye,  or 
eye-lens,  is  a  compound  lens  composed  of  crown  and  flint-glass,  as  in  the  objective. 
Both  are  cemented  together  so  as  to  make  one,  to  prevent  loss  of  light  consequent 
upon  a  ray  passing  from  one  substance  into  another.  In  its  common  form  the  eye- 
lens  is  plano-convex,  with  the  plane  side  nearest  the  eye,  while  the  second  or  field- 
lens  is  double-convex. 

In  the  Steinheil  eye-piece  both  lenses  are  compound,  as  in  the  eye-lens  of  the 
Kellner.  The  parts  of  each  lens  being  cemented  together,  they  form  two  double- 
convex  lenses,  and  therefore  it  may  be  designated  as  an  achromatic  double  eye-piece. 
There  are  some  deviations  in  the  construction  of  the  three  eye-pieces  mentioned 
above,  but  mainly  as  to  the  proper  curvature  of  the  lenses  and  their  proper  distances 
apart,  depending  as  they  do  on  the  index  of  refraction  and  power  of  dispersion 
of  the  glass  used  in  the  construction  of  the  object-glass  and  eye-piece,  but  the 
principle  as  above  explained,  by  which  an  achromatic  image  is  obtained,  underlies 
all  of  them. 

The  Ramsden  eye-piece  is  generally  preferred  on  account  of  its  greater  simpli- 
city and  its  flat  field  of  view,  which  latter  condition  is  more  difficult  to  be  obtained 
with  the  Kellner  and  Steinheil  eye-pieces  in  powerful  telescopes  of  limited  length, 
on  account  of  the  somewhat  larger  field  of  view  possessed  by  these  eye-pieces. 
Moreover,  the  compound  lenses  are  liable  to  be  affected  after  a  while  by  opacities 
caused  by  a  crystallization,  as  it  were,  of  the  cement  uniting  the  parts  composing 
them. 

Objects  seen  through  the  above-mentioned  eye-pieces  are,  however,  inverted, 
and  telescopes  so  constructed  are  often  objected  to  on  this  account.  It  neverthe- 
less is  the  most  proper  telescope  to  use  where  fine  telescopic  measurements  must 
be  made,  as  the  image  is  more  brilliant  than  when  the  objects  are  shown  upright, 
and  it  requires  but  little  practice  to  get  accustomed  to  its  use.  The  inverting  tel- 
escope has  some  other  advantages  that  should  be  mentioned  here.  The  eye-piece 
being  shorter,  an  object-glass  of  greater  focal  length  is  obtained  in  the  same  length 
of  telescope,  thereby  favoring  the  conditions  imposed  to  secure  the  best  definition 
where  the  telescope  must  be  short  and  powerful.  Any  increase  in  the  focal  length  of 
an  object-glass  adds  to  the  magnifying  power  in  the  direct  way,  without  entailing 
the  loss  of  light  consequent  upon  the  use  of  an  eye-piece  made  unduly  powerful. 
On  the  other  hand,  an  increase  in  the  magnifying  power  of  the  eye-piece  magnifies 
the  least  imperfection  that  may  exist  in  the  object-glass,  and  makes  the  cross- 
wires  appear  too  coarse. 


In  practice,  however,  many  engineers  prefer  the  erecting  or  terrestrial  telescope. 
Buch  telescopes  must  be  made  with  an  eye-piece  consisting  of  four  lenses,  as  by 
adding  two  more  lenses,  objects  are  shown  right  side  up,  as  viewed  with  the  naked 
eye.  In  the  construction  of  an  erecting  eye-piece  the  chromatic  aberration  can  be 
corrected  by  the  two  additional  lenses  required  to  secure  an  upright  image ;  but  in 
the  case  of  short  and  powerful  telescopes  the  difficulties  presenting  themselves  to 
secure  a  perfectly  flat  field  of  view  are  very  great,  and  recourse  must  often  be  had 
to  a  compound  lens.  In  the  Kellner  terrestrial  eye-piece  the  third  lens,  reckoning 
from  the  eye,  is  therefore  compound,  and  both  parts  are  cemented  together. 

The  Huyghenian  eye-piece  is  uued  to  a  very  limited  extent  in  the  more  modern 
telescopes  of  instruments  of  precision.  It  is  most  frequently  met  with  in  the 
large  telescopes  used  in  physical  astronomy,  where  objects  are  merely  viewed,  but 
no  measurements  made.  The  field  of  view  is  large,  but  not  quite  flat.  The  amount 
of  light  is  greater  than  in  the  other  eye-pieces.  The  eye-piece  consists  of  two 
plano-convex  lenses  with  their  convex  sides  facing  the  object-glass.  The  main  fea- 
tures are,  that  in  this  eye-piece  the  second  lens  is  placed  between  the  object-glass 
and  its  focus,  and  that  it  brings  the  image  to  a  focus  at  a  point  half-way  between 
the  two  lenses  of  the  eye-piece.  The  focal  length  of  the  second  lens  is  three  times 
larger  than  that  of  the  eye-lens,  and  they  are  placed  apart  at  a  distance  equal  to 
one-half  their  combined  focal  length.  The  image  is  viewed  by  the  eye-lens.  It  is 
called  a  negative  eye-piece,  because  the  image  is  formed  at  a  point  between  the 


The  magnifying  power  of  a  telescope  must  be  proportional  to  the  aperture.  If 
the  magnifying  power  is  too  high  for  the  aperture,  ordinary  objects  will  appear  too 
faint ;  and  if  the  magnifying  power  is  too  low,  the  objects  will  appear  so  small 
that  the  engineer  cannot  point  upon  them  with  sufficient  accuracy. 

The  magnifying  power  should  be  such  that  the  least  perceptible  motion  of  the 
bubble  of  a  level,  or  change  in  the  reading  of  the  verniers,  should  cause  sufficient 
movement  of  the  cross-wires  over  the  object  in  the  field  of  view  to  be  readily  notice- 
able. A  higher  power  than  this  is  worse  than  useless,  since  objects  are  less  brilliant. 

A  lower  power  would  not  develop  the  full  capacities  of  the  instrument.  We  adapt, 
therefore,  the  magnifying  power  and  aperture  of  our  instruments  to  the  sensitiveness 
of  the  levels,  and  the  fineness  of  the  graduation. 

In  our  telescopes  the  main  tube  has  a  much  smaller  diameter  than  is  usual  in  pro- 
portion to  the  size  of  aperture.  This  is  accomplished  without  cutting  off  any  light 
derived  from  the  object-glass,  since  the  pencil  of  light  within  the  telescope  is  contin- 
ually diminishing  in  diameter  until  it  comes  to  a  focus  at  the  plane  of  the  spider- 
lines.  The  danger  of  an  increase  of  reflections  caused  by  bringing  the  interior  surface 
of  the  telescope-tube  nearer  to  this  pencil  of  rays  is  neutralized  by  the  introduction  of 
several  more  diaphragms  properly  placed,  and  by  the  use  of  a  specially  dead  black  coat- 
ing for  the  interior.  By  this  method  of  construction  the  weight  of  the  telescope  is 
greatly  reduced  compared  with  the  large  apertures  used  by  us,  and  therefore  there  is 
less  wear  on  the  horizontal  axis  of  revolution,  and  less  friction  of  the  object-slide. 
There  is,  also,  on  this  account,  less  surface  exposed  to  the  wind,  and  the  instrument  is 
consequently  more  steady. 


Concerning  Apertures  which  are  Abnormally  Large  in 
Proportion  to  their  Focal  Length,  for  the  Telescope 
of  Transits  and  Levels. 

Having  shown  in  the  preceding  article  the  value  of  the  large  apertures  adopted  for 
the  telescopes  of  the  instruments  enumerated  later  in  Part  II,  it  seems  but  natural,  in 
the  desire  to  gain  additional  light,  for  those  unacquainted  with  the  construction  of  these 
telescopes  to  suggest  an  increase  in  the  aperture  of  an  object-glass  given  with  a  partic- 
ular length  of  telescope  and  size  of  instrument, —  that  is,  to  wish  to  go  beyond  what  in 
best  practice  must  be  considered  the  limit  in  diameter  of  aperture  for  a  given  focal 
length.  Good  practice  allows  a  ratio  of  from  1  :  10  to  1  :  12,  —  meaning  that  an  ob- 
ject-glass one  inch  in  diameter  should  have  a  focus  of  from  10  to  12  inches  to  insure 
good  light,  sharp  definition  and  giving  the  natural  magnifying  power  of  the  telescope 
and  not  one  obtained  by  applying  a  too  powerful  eye-piece  and  causing  undue  loss  of 
light. 


33 

In  order  to  reduce  the  size  and  weight  of  field  instruments  and  make  them  more 
portable  and  efficient,  modern  practice  has  been  to  reduce  this  ratio  very  considerably 
by  adopting  as  short  a  focal  length  as  possible,  and  since  the  length  of  telescope  is  the 
chief  factor  in  determining  the  size  of  an  instrument,  as  will  be  seen  by  an  inspection 
of  the  various  instruments  .isted  later  on  in  this  catalogue,  the  resulting  optical  and  me- 
dian ical  conditions  involved  are  of  a  most  difficult  and  strained  character.  Were  these  in- 
struments designed  merely  for  viewing  objects,  asincaseof  binoculars,  operaglasscs,  etc., 
or  for  observing  stars  (which  requires  no  change  of  focus),  so  that  a  short  focussing 
slide  would  be  sufficient,  the  construction  would  be  a  comparatively  easy  task ;  but 
since  these  instruments  are  designed  for  purposes  of  engineering  and  surveying,  where 
angles  between  sighting  poles  and  height:?  of  measuring  rods  must  be  read  at  distances 
which  vary  from  6  feet  to  infinity,  involving  a  continual  change  of  the  focussing  slide, 
it  is  of  the  utmost  importance  that  this  slide-tube  be  of  a  length  which  is  not  only  pro- 
portional to  its  diameter  but  also  sufficiently  long  to  insure  an  accurate  movement  in  a 
straight  line  coinciding  with  the  optical  and  the  geometrical  axes  of  the  telescope, 
since  any  deviation  in  the  motion  of  the  slide-tube  from  a  true  straight  line,  whether 
caused  by  an  insecure  short  slide  or  by  wabbling  or  fretting  due  to  too  much  weight 
at  the  object  end,  will  directly  affect  the  position  of  the  line  of  sight  and  produce 
inaccurate  results. 

Abnormally  Large  Object-Glasses. 

The  foregoing  will  show  some  of  the  difficulties  attending  the  construction  of  short 
telescopes  having  the  largest  apertures  permissible  for  surveying  instruments.  These 
difficulties  are  much  greater  where  a  short  telescope  has  an  abnormally  large  object- 
glass.  In  order  to  accommodate  the  cone  of  light  in  this  case  the  outer  tube  has  to  be 
greatly  enlarged  and  consequently  the  focussing  slide  is  then  too  short  and  out  of  pro- 
portion to  its  diameter,  and  the  greater  weight  attached  to  it  such  that  it  cannot  be 
depended  upon  for  precise  work.  Furthermore  such  telescopes  make  an  instrument 
top-heavy,  enormously  increase  the  wear  on  the  centers  and  on  the  axis  of  revolution 
of  the  telescope,  and  greatly  add  to  the  surface  exposed  to  wind  pressure.  To  over- 
come some  of  these  defects  the  focussing  slide  is  often  placed  at  the  eye-end  of  the 
telescope  for  certain  classes  of  work  where  the  conditions  are  more  favorable,  but  this 
is  impossible  in  the  regular  engineers'  transits,  since  the  eye-piece  must  always 
reverse  through  the  standards,  and  this  cannot  be  done  when  the  slide  is  drawn  out  for 
short  distances. 

So  far  only  the  mechanical  features  involved  in  this  subject  have  been  discussed, 
but  it  may  not  be  amiss  to  mention  that  a  telescope  with  an  abnormally  large  aperture 
and  having  an  abnormally  short  focal  length  very  frequently  lacks  that  sharp  definition 
that  a  smaller  object-glass  will  give.  Therefore  it  is  at  least  questionable  whether  an 
abnormally  large  aperture  has  sufficient  advantage  over  the  usual  large  aperture  to 
warrant  sacrificing  the  longer  object-slide,  its  greater  precision  and  magnifying  power 
that  are  obtained  when  the  focal  length  and  the  aperture  have  their  normal  relation. 
It  should  be  mentioned  also  that  the  special  kind  of  glass  required  for  the  largest  ob- 
jectives has  not  great  power  to  resist  the  effects  produced  by  moisture  in  the  air, 
moisture  from  the  fingers,  etc.,  to  which  it  is  liable  to  be  exposed  in  field  work. 

Hence  it  follows  that  the  use  of  such  abnormal  apertures  should  be  restricted  to 
instruments  for  tunnel  details  or  to  plane-table  alidades'.  In  all  cases  where  larger 
apertures  are  desired,  larger  instruments  with  longer  telescopes  should  be  chosen,  so 
that  the  relation  between  focal  length  and  aperture  may  be  kept  the  same,  and  sharp 
definition,  good  light  and  hi.ch  power  thus  insured.  For  if,  in  a  telescope  of  short 
focal  length,  high  power  is  secured  by  means  of  the  eye-piece,  the  difficulty  in  focussing 
the  wires  becomes  very  marked,  and  is  likely  to  become  a  source  of  annoyance, 
especially  in  the  case  of  the  very  short  eye-piece  used  in  inverted  telescopes.  Further- 
more such  eye-pieces  also  magnify  every  imperfection  of  the  object-glass  as  well  as  of 
the  cross  and  stadia  wires.  This  makes  it  difficult  to  procure  wires  of  sufficient 
fineness,  and  the  increased  danger  of  their  breaking  makes  their  use  almost  prohibitive. 


34 

The  Pancratic,  or  Changeable  Power  Eye-piece  for  the 
Erecting  Telescope 

This  feature,  long  in  use  in  commercial  articles  such  as  field-glasses,  binoculars,  etc., 
can  be  applied,  in  case  of  surveying  instruments,  to  eye-pieces  of  erecting  telescopes 
only,  and  is  then  desirable  only  in  exceptional  cases.  Its  use  in  a  surveying  instru- 
ment cannot  be  considered  a  distinct  gain,  since  it  complicates  the  mechanism  of  the 
telescope — even  in  its  simplest  form — by  the  introduction  of  a  greater  number  of 
pieces,  besides  adding  to  the  weight  of  the  eye-piece.  In  practical  use  it  requires  one 
more  operation  than  the  regular  eye-piece,  but  unless  a  person  is  thoroughly  familiar 
with  it,  not  infrequently  two  more  operations  are  required  when  focussing  on  an 
object.  In  using  it  the  first  operation  will  be  to  set  the  magnifying  power,  by  means  of 
the  movable  lens,  into  the  first  position  marked  for  it ;  the  second,  to  sharply  focus  the 
wires ;  and  the  third,  to  bring  the  object  into  view.  Whenever  the  power  has  been 
changed,  by  accident  or  otherwise,  the  wires  will  have  to  be  brought  again  into  focus 
by  moving  the  whole  eye-piece  in  the  usual  manner.  Owing  to  the  greater  complexity 
of  this  eye-piece  some  of  the  lenses  are  not  readily  accessible  for  cleaning  in  the  field  or 
in  the  office,  so  that  greater  care  is  required  to  preserve  clearness  of  vision.  These 
lenses  are  likely  therefore  to  be  coated  with  a  film  after  exposure,  thus  defeating  the 
very  object  for  which  they  are  designed,  viz.,  to  give  additional  light  by  the  use  of  a  low 
power.  Moreover,  when  applied  to  a  transit  the  focal  length  of  the  object-glass  has  to 
be  shortened  by  about  one-half  inch,  thereby  directly  lessening  the  power  unless  the 
height  of  the  standards  be  increased,  which  of  course  makes  the  instrument  more  top- 
heavy. 

These  are  distinct  disadvantages  in  a  telescope.  The  power  chosen  for  the  tele- 
scope of  a  field  instrument  is  generally  the  one  best  fitted  for  it  and  therefore  should  be 
permanent.  To  make  it  changeable  in  order  to  reduce  this  power  lessens  the  degree  of 
accuracy  with  which  a  measuring  telescope  can  be  pointed  at  a  distant  object,  and  will 
thwart  the  intention  of  the  maker,  who  harmonized  the  power  of  the  telescope  with 
the  sensitiveness  of  the  levels  and  reading  of  the  graduations.  So,  to  reiterate,  it  is 
the  discerning  power  of  a  telescope,  obtained  by  a  normal  aperture  combined  with  a 
sharp  definition  and  high  magnification  of  the  object,  that  will  make  it  possible  to 
quickly  and  accurately  read  graduated  rods  and  see  staffs  at  great  distances.  A  low 
power,  therefore,  would  not  reveal  the  capabilities  of  the  instrument,  and  on  this  ac- 
count the  desire  is  more  often  expressed  to  increase  the  normally  large  power  as 
explained  above  in  order  to  read  close  at  long  range  rather  than  to  have  it  lessened. 

The  aim  of  the  makers  is  to  keep  surveying  instruments  simple  in  design  and  free 
from  incumbrances,  so  that  the  observer's  whole  attention  may  be  given  to  the  work 
before  him.  While  we  do  not  recommend  the  use  of  these  variable  power  eye-pieces, 
when  desired  they  can  be  applied  to  the  larger  size  transits  and  levels  when  made  to 
order. 


The  Graduations. 

Engineers'  transits  have  various  graduations  on  their  circles,  according  to  the 
requirements  of  the  different  branches  of  civil  engineering.  These  various  gradua- 
tions are  read  by  opposite  verniers,  which  may  be  either  single  or  double.  Ameri- 
can instruments  have  usually  double  opposite  verniers,  commonly  reading  the 
circle  to  single  minutes  or  to  thirty  seconds.  For  a  higher  grade  of  work,  required 
in  the  larger  cities  and  on  extended  land  surveys,  they  should,  however*  read  to 
twenty  or  ten  seconds  according  to  size  of  circle. 

Transits  intended  for  triangulation  should  have  only  single  opposite  verniers  and 
one  row  of  figures  clockwise  from  0  to  360°. 

All  instruments  desired  with  graduations  differing  from  those  specified  in  this  cat- 
alogue under  each  style  and  size,  will  be  made  to  order  only. 

The  customary  graduations  of  C.  L.  Berger  &  Sons'  instruments  are  as  follows  :  — 

The  circle  divided  to  half  degrees,      the  verniers  reading  to  single  minutes,  see  Fig.  1. 
ti        <»  u        «<  twenty  minutes,  "          "  "        "  thirty  seconds,    "    Fig.  2. 

<<        ..  ««         »  fifteen  minutes,    "          "  "        "  twenty  seconds,  "    Fig.  3. 

«        ««  "         "  twenty  minutes,    "          "  "        "  twenty  seconds,  "    Figs.  4, 5  and  6 

«i       K          «»        "  ten  minutes,          "          "  "        "  ten  seconds,         "    Fig.  7. 


35 

To  express  the  relation  between  the  vernier  and  circle  divisions,  let  d=the  rn  tu« 
of  one  division  of  the  circle;  d'=the  value  of  one  division  of  the  vernier;  d-d'=» 
the  least  count  of  the  vernier,  or,  in  other  words,  the  smallest  reading  of  the  circle. 

n=  the  number  of  spaces  of  the  vernier  which  correspond  to  (n  —  1)  spaces  of 
the  circle. 

We  then  have  the  three  formulas ; 


(1.) 
(20 
(3.) 


d— d'= 


Thug,  for  example,  suppose  the  circle  was  divided  to  15',  and  it  was  desired  to 
read  to  20".    Here,d=15' 


d — d',  or,  the  least  count: 
Then,  by  formula  (1) 

n  • 


=45 


Therefore,  45  spaces  of  the  vernier  must  correspond  to  44  or(n-l)  spaces  of  the 
circle. 

Suppose  again  the  arc  to  be  divided  to  2CK,  and  to  be  read  to  30".    In  this  case 
we  have 


Therefore,  40  spaces  of  the  vernier  must  correspond  to  39,  or  (n  —  1)  spaces  of 
the  circle.  These  are  the  graduations  which  Messrs.  C.  L.  Berger  &  Sons  usually 
adopt  for  engineers'  transits. 


2.2.0 

The  cut  fihows  a  portion  of  the  circle  and  vernier,  to  illustrate  the  method  of 
reading  to  thirty  seconds. 

The  lines  marked  130, 140,  and  150  denote  10°  each.  The  shorter  lines  half  way 
between  them  denote  135°  and  145°.  The  next  shorter  lines  denote  whole  degrees, 
while  the  shortest  lines  are  one-third  of  a  degree,  or  20/  apart. 

The  vernier  comprises  the  upper  series  of  lines.  Of  this  series  only  that  half 
lying  to  the  right  of  the  vertical  arrow,  or  zero,  and  having  the  figures  10  and  20 
inclined  in  the  same  direction  as  the  130, 140,  and  150  of  the  arc,  is  to  be  used  in 
connection  with  these  figures.  The  vernier  is  double, — one  half  to  be  used  with 
one  set  of  graduations  of  the  arc,  the  other  half  to  be  used  when  angles  are  laid  off 
in  the  opposite  direction,  and  then  the  lower  set  of  figured,  210, 220,  and  230  are  used. 

It  is  to  be  especially  remembered  that  the  figures  on  the  vernier  are  inclined  in 
the  same  direction  as  the  figures  on  the  arc  to  which  they  belong. 

To  read  the  vernier,  first  note  the  whole  degrees,  and  207  spaces  lying  between 
the  last  10  degree  division  and  the  zero  division  of  the  vernier. 

Thus  in  the  cut,  using  the  upper  line  of  figures,  the  zero  of  the  vernier  has  passed 


the  130°  division,  and  moved  on  until  it  is  between  the  20"  and  40'  space  beyond  the 
138°  mark.    The  first  part  of  our  reading  will  therefore  be  138°  20'. 

Second,  look  along  the  vernier,  beginning  from  the  zero  point,  and  in  the  direc- 
tion in  which  the  graduation  of  the  arc  runs,  until  one  line  of  tiie  vernier  is  found 
which  seems  to  be  a  prolongation  of  an  opposite  line  on  the  arc. 

Consider  each  of  the  vernier  spaces  between  the  vernier  zero  and  such  a  line, 
as  equal  to  30"  of  arc. 

Add  the  number  of  minutes  and  seconds  thus  obtained  to  the  first  reading.  The 
result  will  be  the  reading  of  the  circle. 

Thus  we  notice  that  the  vernier  zero  is  a  trifle  over  half-way  of  the  distance 
between  the  207  and  40'  marks  of  the  arc. 

And  looking  along  the  vernier  to  the  right,  we  notice  that  the  lines  of  the  ver- 
nier gradually  approach  the  lines  on  the  arc  until  the  twentieth  line  of  the  vernier 
is  precisely  opposite  a  line  on  the  arc.  Of  course,  since  each  vernier  space  denotes 
30",  the  alternate  ones  made  a  little  longer  in  the  cut  will  denote  single  minutes, 
and  on  the  vernier  therefore  the  twentieth  line  would  correspond  to  10'  00",  and 
since  our  first  reading  was  between  20'  and  40',  this  vernier  reading  is  to  be  added 
to  that  first  reading. 

Thus,  138°    20' 

10'    00" 

138°    30'    00"   will  be  the  reading  of  the  vernier, 

using  the  upper  graduation. 

In  the  same  manner  we  proceed  to  the  left  in  reading  the  lower  graduation,  in 
which  the  figures  are  inclined  to  the  left.  Thus  in  the  cut,  we  should  find  the  zero 
point  of  the  vernier  is  beyond  the  221°  20'  mark,  and  the  line  of  the  vernier,  which 
it  seemingly  a  prolongation  of  a  line  of  the  arc,  corresponds  to  W  00".  Then  we 
hare  221°  20' 

10'    00" 


221°  30"  00"  for  the  reading  of  the  vernier,  using 
the  lower  graduation. 

Practically,  in  reading  the  vernier,  the  engineer  decides  which  line  is  in  coinci- 
dence by  the  position  of  the  lines  on  both  sides. 

He  first  notices,  roughly,  what  fractional  part  of  a  space  on  the  limb  lies  between 
the  vernier  zero  and  the  last  graduation  mark  it  has  passed.  This  enables  him  to 
look  immediately  to  that  part  of  the  vernier  in  which  the  coincidence  occurs. 

Thus  in  the  figure  the  vernier  zero  is  about  half  way  between  221°  20'  and  221°  40% 
the  engineer  therefore  immediately  looks  about  half  way  along  the  vernier  and 
finds  the  10'  00"  division  to  be  the  one  sought. 

When  the  graduation  is  to  thirty  seconds,  the  engineer  will  find  that  if  he  only 
chooses,  lie  can  work  to  minutes  with  this  graduation  quite  as  rapidly  as  with  a 
transit  graduated  to  minutes,  by  simply  disregarding  the  shortest  lines  of  the  vernier. 

The  second  vernier,  which  is  distant  180°,  or  exactly  opposite  the  one  read  first, 
may  also  be  read.  Not  so  much  to  eliminate  any  eccentricity  of  the  circle  and  ver- 
niers as  to  afford  a  valuable  check  upon  the  angle  measured. 

Greater  accuracy  in  the  measurement  of  any  angle  may  be  obtained  by  the 
principle  of  repetition.  In  this  case,  before  and  after  an  angle  has  been  repeated  a 
number  of  times,  all  four  of  the  verniers  should  be  read,  and  if,  for  example,  the 
graduations  proceed  from  right  to  left,  the  left  hand  side  of  each  double  vernier 
should  be  read  as  usual ;  but  hi  the  right  hand  side  the  line  now  marked  20  on  the 
vernier  should  be  considered  0,  and  the  arrow  on  the  vernier  20.  Then,  with  this 
convention,  only  the  minutes  and  seconds  of  the  second  vernier  should  be  used. 

But  it  should  be  here  remarked  that  the  repetition  of  angles  is  not  now  hold  in 
such  repute  by  our  best  engineers,  as  it  was  before  the  present  perfection  of  the  art 
of  graduating  and  centering  the  circles  and  verniers  of  engineering  instruments. 

The  engineer  who  has  not  used  them  will  find  the  ground-glass  shades  a  great 
convenience  in  reading  the  vernier.  They  are  so  placed  as  not  to  be  readily  broken, 
and  they  shed  a  clear,  white  light  upon  the  graduations. 

Graduations  on  solid  silver  are  much  to  be  preferred  to  graduation*  on  any 
known  brass  alloy.  The  surface  of  the  silver  can  be  worked  very  plane,  since  it  is 
of  uniform  texture.  The  graduations  can  be  cut  with  the  utmost  uniformity  In 
width  of  line  and  spacing. 

The  graduations  on  a  BERGER  Transit  are  not  mere  scratches  on  German 
Silver ;  they  are  extremely  accurate,  have  great  depth  of  line,  and  are  clearly 
cut  and  on  925/lOOOths  Sterling  Silver,  being  easily  read,  even  in  a  faint  light ; 
the  lines  are  of  just  the  proper  length  so  as  not  to  be  fatiguing  to  the  eye. 

The  figuring  of  the  circles  and  verniers  is  unusually  distinct. 


The  Customary  Graduations  of  Circles  and  Verniers 
for  C.  L.  Berger  &  Sons'  Instruments. 

Figures  1,  2,  3  and  4  illustrate  graduations  in  which  the  horizontal  circles  have  two 
rows  of  figures,  from  0°  to  830°,  in  opposite  directions.  The  figures  in  the  main  row 
nearer  the  vernier  increase  clockwise,  and  in  the  other  row  increase  in  the  opposite 
direction,  so  that  angles  may  be  read  rapidly  in  either  direction.  Other  figuring,  such 
as  0°  to  90°  to  0°,  0°  to  180°  to  0°,  will  be  made  when  specially  ordered. 

The  vertical  semicircle  is  figured  from  0°  to  90°  in  either  direction  for  reading  angles 
of  elevation  or  depression,  and  the  full  vertical  circle  from  0°  to  90°  to  0°.  For  astro- 
nomical work  the  vertical  circle  will  be  figured  clockwise  from  0°  to  360°  when  spe- 
cially ordered. 

Whenever  a  change  is  desired  from  the  customary  figuring,  as  given  below,  a  diagram 
should  be  sent  with  the  order. 

The  size  of  circle  appropriate  with  the  various  graduations  and  verniers  will  be  found 
in  the  description  and  extras  of  instruments  in  the  catalogue  and  are  the  ones  recom- 
mended. A  larger  size  of  circle  than  the  one  enumerated  with  the  instrument  would 
often  prove  of  no  value,  while  a  smaller  size  may  prove  fatiguing  to  the  eye  to  read. 

The  cuts  below  represent  a  graduation  on  a  circle  13  inches  in  diameter. 


Graduation  Reading:  to  Minutes. 


50 


w 


360 


Fig.  I. 


Fig.  1.  Circle  divided  into  30'  spaces. 

Double  Opposite  Verniers  to  Horizontal  and  Vertical  Circles,  also  for  arcs  (29  spaces 
into  30)  reading  to  single  minutes. 

Note.- 

ing  folding 

its  zero  point  in  the  center  and  extends  15'  each  way.  In  reading  this  vernier,  proceed  to  the  right  or 
left  on  the  upper  row  of  figures  in  the  direction  of  the  graduation  used,  and  if  the  coincident  line 
is  not  found  before  reaching  the  15'  line,  continue  on  the  lower  fine  of  figures  on  the  other  half  of 
the  vernier,  so  that  the  whole  graduation  from  (X  to  3<y  lies  in  the  same  direction. 


. — Sometimes  when  for  want  of  space  in  some  particular  type  of  instrument  a  single  read- 
ig  vernier  must  be  applied  to  a  circle  figured  in  opposite  directions  the  single  vernier  has 
its  zero  point  in  the  center  and  extends  15'  each  way.   In  reading  this  vernier,  proceed  to  the  right  or 


Graduation  Reading  to  3O". 


280 


Fig.2. 


Fig.  2.  Circle  divided  into  20'  spaces. 

Double  Opposite  Verniers  to  Horizontal  Circle  (39  spaces  into  40)  reading  to  30". 


38 


Graduation  Reading  to  2O". 

A 


15 


J50 


J60 


Fig.  3. 

Usual  Style  of  20"  Verniers  for  the  Engineer's  Transit. 

Fig.  3.  Circle  divided  into  15'  spaces. 

Double  Opposite  Verniers  to  Horizontal  Circle  (44  spaces  into  46)  reading  to  20". 

Note. —  In  figure  3  the  lines  on  both  the  circle  and  the  verniers  are  considerably  closer  than  in 
those  of  figure  2.  For  this  reason  it  will  be  seen  that  this  graduation  is  more  fatiguing  to  the  eye  to 
read.  However  this  form  is  the  only  feasible  one  for  the  vernier  opening  when  two  rows  of  figures 
with  zero  in  center  of  vernier  are  required,  as  in  general  engineering  work  where  angles  are  to  be 
read  rapidly  to  right  and  left.  For  the  best  vernier  for  triangulation  transits  see  figures  4  and  5. 


Graduation  Beading  to  2O". 


.4. 


For  the  Engineer's  Transit  intended  for  Triangulation.    Made  to  order  only. 

Fig.  4.  Circle  divided  into  20'  spaces. 

Single  Opposite  Verniers  reading  to  20"  (59  spaces  into  60);  two  zero  points  to  Ver- 
niers ;  two  rows  of  figures. 

Note. —  This  vernier  has  wider  spacing  on  the  circle  and  on  this  account  is  more  easily  read  to 
20",  but  has  the  disadvantage  that  when  an  engineer  wants  double  opposite  verniers,  as  shown  in  the 
verniers  Figs.  1, 2,  and  3,  the  opening  of  the  vernier  plate  would  have  to  be  twice  as  long  and  there- 
fore too  large  for  the  superstructure  of  the  instrument.  It  is  desirable  in  such  cases  where  an  en- 
gineer wants  a  20"  graduation  on  above  limb  with  two  rows  of  figures  to  provide  verniers  with 
two  zeros,  one  at  each  end,  as  shown  above,  necessitating  the  inconvenience  of  first  shifting  the  ver- 
nier plate  from  one  zero  to  the  other  before  angles  can  be  read  in  the  opposite  direction. 

This  difficulty  may  be  avoided,  however,  by  using  the  10'  mark  on  the  vernier  as  the  zero  point 
and  reading  angles  in  either  direction  as  explained  under  figure  6. 


Graduation  Heading  to  2O". 

A 


Usual  Style  Vernier  for  Transits  intended  for  Triangulation.  —  Made  to  order  only. 

Fig.  5.   Circle  divided  into  20'  spaces. 

Single  Opposite  Verniers  reading  to  20"  (59  spaces  into  60).     One  row  of  figures. 


Graduation  Reading  to  2O". 

A 


Fig.  6. 

Folding  Vernier.    Made  to  order  only. 

Fig.  O.  Circle  divided  into  20'  spaces  same  as  Nos.  4  and  5. 

Single  Opposite  Verniers  having  one  zero  point  in  center  with  two  rows  of  figures. 

Note. —  With  this  style  of  single  vernier  angles  may  be  read  to  left  or  right.  If  angles  are  being 
read  clockwise  start  with  the  zero  point  under  A  and  continue  to  the  left  until  the  10'  mark  is 
reached,  then  if  no  coincidence  is  found,  continue  by  taking  the  1(X  mark  at  the  opposite  end  of  the 
vernier  (right  end)  and  reading  toward  the  2(X  mark.  In  reading  angles  in  the  opposite  direction  use 
the  figures  which  slope  toward  the  right. 


Graduation  Reading*  to  1C"  (on  a  7  or  8-inch  Circle). 


Fig.  7. 


Usual  Style  of  Verniers  for  Triangulation. 

Fig.  7.  Circle  divided  into  10'  spaces. 
Single  Opposite  Verniers  reading  to  10"  (59  spaces  into  60). 

Whenever  desired  double  opposite  verniers  can  be  furnished,  with  two  rows  of 
figures  on  limb  from  0°  to  360°  in  opposite  directions. 

Note.  —  In  cases  where  less  weight  and  greater  compactness  and  portability  of  instrument  are 
desirable,  as  in  instruments  often  furnished  to  the  Government  for  use  in  mountains  and  in  the 
tropics,  a  10"  graduation  can  be  placed  upon  a  6#  inch  circle.  The  spacing  however  is  very  close, 
and  while  this  size  of  circle  will  give  almost  equally  as  accurate  results,  its  reading  must  neces- 
sarily prove  more  fatiguing  to  the  eye. 


Graduation  Reading  to  5"  on  8-inch  Circle. 

Sometimes  it  is  requested  to  graduate  an  8-inch  circle  to  read  to  6"  direct,  when  the 
circle  will  be  divided  into  5'  spaces  and  the  vernier  59  spaces  divided  into  60  parts.  As  a 
rule  this  r^aduation  is  not  desirable  for  vernier  instruments  on  account  of  the  close 
spacing  on  circle  and  verniers  which  of  necessity  must  prove  inconvenient  in  usual  en- 
gineering practice  because  of  its  greater  liability  to  error  in  reading. 


Decimal  Vernier  Graduation. 

For  railroad  work  it  is  sometimes  requested  to  graduate  vernier  A  to  read  to 
minutes  or  30",  as  usual,  and  vernier  B  to  read  to  T£pth  of  a  degree. 

If  the  circle  is  to  read  to  minutes,  vernier  A  will  be  as  shown  in  figure  1.  A 
decimal  vernier  for  this  graduation  requires  49  spaces  of  the  circle  to  be  divided  into 
50  parts  on  the  vernier,  making  a  very  long  vernier,  so  that  there  is  only  room  for  a 
single  vernier  in  the  opening  of  the  vernier  plate.  This  vernier  would  either  have  two 
zero  points  as  in  figure  4,  or  would  have  the  zero  at  the  center,  as  shown  in  figure  6. 

If  one  vernier  is  to  read  to  30"  and  the  other  to  T^th  of  a  degree,  the  circle  would 
be  divided  into  15'  spaces,  and  the  A  vernier  would  be  as  shown  in  figure  9.  The 
decimal  vernier  for  this  graduation  requires  24  spaces  of  the  circle  to  be  divided  into  25 
parts  on  the  vernier  as  shown  in  figure  8. 

The  disadvantages  of  such  graduations  are,  first,  that  the  spacing  of  the  circle  is  too 
doss  for  rapid  reading,  and  second,  that  mistakes  are  liable  to  be  made  in  reading  the 
verniers  by  confusing  the  30"  reading  of  vernier  A  with  the  T^th  of  a  degree  of 
vernier  B.  Another  disadvantage  is  that  when  it  is  desired  to  read  both  verniers, 
A  and  B,  as  in  repeating  angles,  this  cannot  be  conveniently  done  with  either  of  the 
above  arrangements.  For  these  reasons  the  two  verniers  A  and  B,  should  have  the 
same  graduation. 

There  are  occasionally  inquiries  for  transits  provided  with  decimal  vernier  gradua- 
tion. These  can  be  furnished  when  desired,  but  must  be  specially  made  to  order.  On 
account  of  the  great  length  of  the  double  vernier,  single  opposite  verniers  of  the  fold- 
ing pattern  (fig.  6)  are  the  only  feasible  ones.  Although  objections  are  often  raised 
against  them,  still  many  engineers  like  folding  verniers  after  becoming  accustomed  to 
them. 

Decimal  Vernier  Graduation. 


10 


8. 


r.  8.  Circle  divided  into  15'  spaces. 
Double  vernier  (24  spaces  into  25)  reading  to  hundredths  of  a  degree. 


Graduation  Heading  to  3D". 

On  same  limb  with  B  vernier  to  read  to  lOOths  of  a  degree  as  in  Fig.  8,  and  A  ver- 
nier reading  to  30". 


360 

Fig.  9. 

.  9.   Circle  divided  into  15'  spaces. 

Double  vernier  A  (29  spaces  into  30)  reading  to  30". 
of  a  degree. 

This  vernier  is  not  commonly  used,  but  has  the  advantage  that  the  double  vernier 
occupies  only  a  short  space. 


B  vernier  reading  to  lOOtns 


41 


Graduation  Reading  to  Hundredths  of  a  Degree. 

A 


\o 


Fig.  1O.  Circle  divided  into  30'  spaces. 

Single  vernier  (49  spaces  into  50)  reading  to  hundredths  of  a  degree. 

Two  Zero  Points  to  Verniers  ;  Two  Rows  of  Figures. 


Inclination  and  Color  of  Figures  for  Graduations. 

All  of  the  double  verniers  shown  above  require  the  limb  to  be  provided  with  two 
sets  of  figures  in  black,  as  indicated  in  the  diagrams  and  further  illustrated  in  the 
diagrams  of  the  various  limbs  on  the  following  page.  To  prevent  mistakes,  the 
figures  of  each  row  are  inclined  in  the  direction  in  which  the  ver- 
niers must  be  read.  It  will  be  noticed  that  the  figures  above  are  inclined  only 
enough  to  easily  distinguish  each  row  from  the  other.  If  the  figures  are  inclined  at  too 
great  an  angle  their  distinctness  would  be  impaired  and  considerable  difficulty  would 
be  experienced  in  reading  them  correctly,  and  would  be  apt  to  lead  to  gross  errors. 
The  shape  of  the  above  figuresis  very  plain,  so  as  to  standout  clearly.  If  desired,  the 
figures  of  the  contra-clockwise  row,  with  the  figures  of  its  corresponding  verniers,  and 
those  of  the  vertical  circle,  can  be  furnished,  without  extra  cost,  in  a  red  color,  to  further 
distinguish  them  from  the  clockwise  graduations.  There  is,  however,  no  advantage 
in  the  red  over  the  black  figures,  since  the  latter  stand  out  very  plainly  on  a  silver  sur- 
face, and  are  very  distinct,  even  after  the  silver  has  somewhat  tarnished,  is  soiled,  or 
when  the  graduations  must  be  read  in  a  faint  or  artin'cal  light,  where  the  red  figures 
will  not  show  a  marked  contrast  to  the  black. 

If  red  figures  are  desired,  the  code  word  "Reddish"  must  be  used,  and  such 
Transits  will  have  to  be  especially  made,  not  being  kept  in  stock. 


42 


Figuring  of  Graduations. 


HORIZONTAL  CIRCLE 


HORIZONTAL  CIRCLE 


DIAGRAM     Q 

CODE:  SAPPHIRE 


HORIZONTALClRCLE 


HORIZONTAL  CIRCLE 


Bin- WITH  ZtROSjSOViBWT 


CO**SSVAMAT)OMraM6  WITHTVP ROWS  orncuRCS: 


COMPASS  RING  neuRto 


AS5UPf»UtDV«THTRANSrr3 


WITH  CARDINAL  POINTS  ENGRAVED  ON 


^  \  VLRTICALClRCLtr»u«OlNQUAORANT5 


43 

The  Centers. 

Quite  as  important  as  the  graduation,  is  the  exact  fitting  of  what  the  makers 
call  the  centers  of  the  instrument;  i.e.,  the  two  vertical  metafaxis,  about  which thl 
circle  and  the  vernier  plate  turn. 

Both  axes  must  be  exactly  concentric  with  the  center  of  the  graduated  oirclp 
and  the  center  of  the  horizontal  axis  of  the  telescope  in  any  position  of  the  instru- 
ment. The  most  sensitive  level  about  the  instrument  should  not  show  anv  disnlace- 
ment  when  the  circle-plate  is  held,  and  the  lower  plate  moved  by  the  hand 

In  the  construction  of  the  inner  center,  the  hardest  bell-metal  should  be  used 
and  for  the  outer  center  a  red  composition  metal  of  the  best  quality.  To  insure  a 
true  concentricity  of  the  axis,  and  consequently  of  the  limb  and  vernier  it  is 
necessary  that  they  should  each  be  turned  in  a  dead  center  lathe,  each  about  its 
own  axis.  In  fitting  the  centers,  they  should  turn  without  the  slightest  play,  and 
yet  with  very  little  friction. 

We  take  the  precaution  of  casting  the  outer  center,  circle  and  vernier  plate  in  the 
same  mould,  to  avoid  any  difference  in  the  composition  of  the  metal. 

The  upper  plate  should  not  be  hammered,  since  this  would  also  effect  an  unequal 
expansion  of  the  metals  in  extreme  temperatures,  causing  the  vernier  to  read  too 
long  or  too  short. 

After  the  plates  are  put  together,  the  vernier  and  limb  should  revolve  in  the 
same  plane,  to  avoid  parallax.  The  space  between  the  limb  and  vernier  should 
have  the  appearance  of  a  uniform,  fine,  black  line. 


The  Compass. 

In  running  old  lines,  and  as  a  check  in  running  new  ones,  the  compass  is  frequent- 
ly a  very  important  part  of  the  transit.  Its  needle  should  be  fcnm|tc.rr.<|  throughout, 
and  of  hard  steel,  to  retain  its  magnetism.  It  should  be  thin,  and  y«»t  at  tho  game 
time  have  enough  surface  to  be  strongly  magnetic.  It  should  be  swung  upon  a 
iewelled  center,  and  so  nicely  fitted  that  when  at  rest,  with  the  instrument  levelled, 
the  two  extreme  points  should  just  clear  the  graduation  of  the  compass  box,  and 
read  precisely  180°  different  in  any  part  of  the  graduated  arc.  The  pivot  on  which 
it  swings  should  be  conical,  and  hardened  so  that  it  may  swing  upon  a  sharp  point, 
without  having  this  point  weak. 

The  needle  should  also  be  so  sensitive,  that  when  drawn  from  its  pointing  by 
the  outside  attraction  of  a  piece  of  iron  held  in  the  hand  a  foot  or  so  away,  it  will 
settle  to  the  same  reading  several  times  in  succession. 

This  sensitiveness  depends  upon  the  form  and  sharpness  of  the  pivot,  the  strength 
of  its  magnetism,  and  its  bearing  on  the  jewelled  center. 

If  it  should  be  found  that  a  needle  has  lost  its  sensitiveness,  it  is  probably  not 
BO  much  owing  to  its  loss  of  magnetism,  as  to  a  dulling  of  the  pivot.  Since  this 
may  happen  when  the  engineer  is  without  access  to  the  maker,  and  an  instrument 
otherwise  be  in  good  condition,  it  should  be  remarked  that  the  pivot  can  be  sharp- 
ened after  removing  the  needle,  by  taking  a  fine  oil-stone,  and  while  turning  the 
instrument  with  one  hand,  grinding  the  pivot,  with  the  oil-stone  in  the  other ;  being 
careful  to  incline  the  grinding  surface  about  25°  to  the  pivot.  The  pivot  is  origi- 
nally turned  and  sharpened  in  a  lathe,  and  in  grinding  by  hand,  great  care  should 
be  taken  to  preserve  its  conical  form. 

The  two  extreme  points  which  lie  next  the  graduation,  together  with  the  point 
of  suspension,  should  lie  in  one  straight  line. 

The  center  of  gravity  of  the  needle  should  be  as  far  below  this  line  as  possible. 

The  quivering  of  a  needle  so  constructed  is  not  annoying,  since  the  center  of  its 
quivering  motion  is  in  the  line  through  its  two  extreme  points,  which  are,  therefore, 
stationary. 

To  determine  whether  the  transit  itself  has  any  iron  in  it  to  disturb  the  needle, 
it  is  a  good  plan,  after  setting  the  instrument  so  that  both  compass-needle  and 
vernier  reads  0°,  to  go  round  the  circie,  setting  the  vernier  ten  degrees  ahead  each 
time,  and  noting  whether  the  compass-needle  also  describes  an  arc  of  precisely  ten 
degrees.    If  it  does  not.  there  is  some  local  attraction. 

The  graduations  on  the  compass  box  should  begin  at  the  North  point,  and  run 
90°  in  both  directions ;  then  decrease  to  0°  again  at  the  South  point.  In  mine 
transits  a  second  continuous  row  from  0°  to  360°  starting  at  North  is  placed  on 
the  compass  ring.  Other  figurings  are  made  especially  to  order.  In  order  that 
the  needle  reading  may  indicate  the  direction  of  the  telescope,  the  line  joining  the 
>eros  of  the  ordinary  compass  ring  must  be  in  the  same  vertical  plane,  with  the 


44 

line  of  collimation  of  the  telescope ;  and  the  letters  denoting  the  cardinal  points, 
East  and  West,  must  be  transposed;  i.  e.,  when  the  letter  N  is  towards  the  North, 
the  letter  W  should  be  towards  the  East.  Of  course  the  needle  indicates  magnetic 
north,  and  in  the  case  of  instruments  unprovided  with  means  of  setting  off  the  local 
variation  of  the  needle,  all  the  readings  of  the  needle  must  be  corrected  for  this 
local  deviation. 

If  the  transit  is  provided  with  a  variation  plate  and  it  is  desired  to  set  off  the  varia- 
tion by  means  of  the  horizontal  plate  closer  than  half  and  quarter  degrees say  to 

minutes  —  this  can  be  done  on  the  horizontal  circle.  The  verniers  of  the  Transit  are 
set  at  zero  of  the  graduation  and  clamped.  The  zero  of  the  variation  ring  must  also 
be  made  to  coincide  with  the  stationary  pointer.  The  needle  is  then  released  and 
when  at  rest  the  zeros  of  the  variation  ring  must  be  made  to  coincide  with  the  needle 
ends  by  the  lower  tangent  screw.  To  set  off  the  variation,  the  vernier  plate  clamp  is 
released  and  the  vernier  plate  turned  so  that  the  telescope  (pointing  Korth)  moves 
toward  the  actual  East  if  the  variation  is  West,  and  toward  actual  West  if  the  varia- 
tion is  East,  until  the  vernier  reads  the  desired  declination  on  the  horizontal  circle. 
The  zero  of  the  variation  ring  is  now  brought  to  coincide  with  the  needle  ends  and  the 
telescope  will  be  pointing  to  the  true  North. 

If  great  accuracy  is  not  desired,  the  variation  may  be  set  off  directly  on  the  variation 
ring  in  the  following  manner :  If  the  variation  is  East,  move  the  zero  point  of  the 
shifting  compass  ring  the  amount  of  variation  for  the  locality  toward  the  astronomical 
East  (or  toward  the  transposed  W.  point  in  the  bottom  of  the  compass  box).  Then 
clamp  shifting  ring.  When  the  N.  point  of  needle  reads  0  on  the  graduated  ring 
the  telescope  will  then  be  pointing  to  the  true  North.  If  the  declination  is  West,  turn 
the  shifting  ring  the  proper  amount  toward  the  astronomical  West,  or  toward  E. 
point  in  bottom  of  compass  box. 

The  variation  plate  of  our  Transits  with  yoke  standard  frame  has  a  rack  and  pinion 
motion  with  a  capstan-headed  nut  for  clamping  when  in  position.  To  operate  it, 
slightly  unscrew  the  capstan -h  jaded  nut  at  side  of  milled  head,  set  off  the  variation, 
and  then  again  clamp  this  nut  tightly. 


Spirit-Levels. 

The  spirit  levels,  as  regards  their  sensitiveness,  should  be  in  strict  keeping  with 
the  optical  power,  and  the  graduations  of  the  instrument,  but  the  quality  should  be 
of  the  best.  A  level-bubble  should  move  uniformly  over  the  same  distance,  when 
the  telescope  is  made  to  point  on  two  objects  alternately,  differing  slightly  in  alti- 
tude, by  the  leveling  screws  alone.  In  change  of  temperature  the  bubble  should 
lengthen  symmetrically  from  the  center ;  and  no  matter  what  its  length,  it  should 
move  quickly,  without  any  of  the  hitching,  which  is  caused  usually  by  a  little  d-'rt 
introduced  when  it  is  filled. 

Of  the  three  levels  attached  to  the  complete  transit,  the  telescope  level  is  the 
most  sensitive.  It  should  be  sensitive  enough  for  ordinary  leveling,  such  as  good 
railroad  work.  The  level  in  front,  or  at  right  angles  to  the  standards,  should  be 
sensitive  enough  to  make  a  line  plumb  by  it  to  any  height ;  while  the  third  lev**1 
on  the  standard  is  used  in  leveling  up  the  instrument,  and  to  establish  the  7*** 
point  for  the  vernier  correctly  when  vertical  angles  must  be  measured. 

The  test  of  the  fitness  of  the  various  levels  for  the  capacity  of  the  instrument 
should  lie  in  this :  that  after  carefully  bi-secting  an  object  in  the  field  of  view,  in 
such  a  position  of  the  instrument  that  all  the  levels  can  be  read,  and  then  slightly 
deranging  them  all  with  the  leveling  screws,  the  bi-section  will  be  accurately  made 
after  restoring  the  levels  to  the  exact  position  they  before  occupied,  by  the  leveling 
screws  a^one. 

Leveling  Screws. 

Messrs.  C.  L.  Berger  &  Sons  usually  cut  their  leveling  screws  with  32  threads  to  an 
inch  provide  the  usual  four  screws  in  opposing  pairs.  The  plates  once  set  firmly 
apart  by  tightening  two  of  these  screws  on  the  same  side,  the  leveling  of  the  instru- 
ment is  easily  accomplished  by  turning  the  two  screws  of  an  opposing  pair  so  that 
both  thumbs  shall  move  toward  each  other  (when  the  bubble  will  go  toward  the 
right),  or  both  thumbs  away  from  each  other,  when  the  bubble  will  move  toward 
the  left.  Instruments  intended  for  triangulation,  i.  e.,  reading  to  10"  or  less,  should 
however  be  supported  on  three,  instead  of  upon  four  screws.  In  this  case  the  in- 
strument is  rapidly  leveled  by  bringing  one  level  parallel  to  two  of  the  screws,  the 
other  level  will  now  be  at  right  angles  to  it.  Level  both  levels  at  the  same  time 
by  turning  one  of  the  screws  to  which  the  first  level  is  parallel  and  the  screw 
which  is  at  right  angles  to  this  level.  Of  course  the  instrument  may  now  be 
reversed  to  guard  against  non-adjustment  of  the  levels. 


45 

Three  Leveling:  Screws  versus  Four. 

To  the  student  of  the  progress  in  Engineers'  field  instruments,  the  question  often 
presents  itself  as  to  the  comparative  merits  of  an  instrument  provided  with  three, 
over  one  having  four  leveling  screws.  It  should  be  here  remarked  that  the  greater 
portability  existing  in  instruments  provided  with  four  leveling  screws  still  com- 
mends itself  to  all  using  the  more  customary  class  of  instruments.  However,  the 
finest  class  of  field  instruments,  requiring  spirit-levels  corresponding  to  the  fine- 
ness of  graduation,  cannot  be  advantageously  manipulated  with  tour  leveling 
screws.  The  results  thus  obtained  would  be  little  better  than  those  obtained  with 
a  more  ordinary  instrument.  To  insure  the  full  benefit  of  a  finer  instrument,  such 
as  used  in  triangulation,  the  maker  will  prudently  apply  three  leveling  screws, 
mounted  on  a  feasts  larger  then  is  usual  in  instruments  with  four  screws.  So,  while 
four  leveling  screws  have  the  advantage  of  greater  compactness  and  less  weight 
three  screws  have  the  advantage  for  closer  setting,  giving  better  results.  The 
maker  will  therefore  adapt  either  the  one  or  the  other  kind  to  his  instruments  aa 
the  c*se  may  require. 


Quick  Leveling  Attachment. 

[For  illustration  seepage  118.] 

As  all  devices  of  this  kind  detract  more  or  less  from  the  stability  of  an  instru- 
ment, it  seems  they  never  have  been  regarded  with  much  favor  by  the  engineering 
profession  at  large.  There  are  cases,  however,  where  the  use  of  such  a  device,  in 
a  mountainous  country,  or  in  underground  work  of  a  close  character,  becomes  very 
desirable.  Messrs.  C.  L.  Berger  <fc  Sons'  device,  unlike  devices  of  a  similar  kind  form- 
ing a  part  of  the  instrument  proper,  consists  of  a  coupling  with  a  ball  and  socket  joint 
which  can  be  screwed  between  the  instrument  and  tripod.  As  this  intermediate 
piece  forms  no  part  of  the  instrument  itself  it  can  be  readily  attached  or  detached 
at  will,  thus  adapting  the  instrument  to  the  circumstances  and  to  the  class  of  work 
in  hand.  For  this  purpose  the  threads  of  this  coupling  or  quick-leveling  attach- 
ment,  and  those  of  the  instrument  and  tripod  are  identical ;  and  as  all  their  transits 
and  levels  with  four  leveling  screws  are  interchangeable  on  any  of  their  tripods, 
one  such  coupling  is  sufficient  for  an  engineer's  outfit.  In  fact  one  extra  tripod 
permanently  provided  with  this  quick-leveling  attachment  may  be  kept  ready  for 
occasional  use  in  an  office  where  there  are  a  number  of  their  instruments. 

To  use  this  quick-leveling  attachment  proceed  as  follows: — Screw  it  to  the 
instrument,  and  then  screw  both  to  the  tripod  in  the  usual  manner,  taking  care 
that  the  coupling  becomes  firmly  fastened  thereto.  Now  to  operate  it,  slightly 
unscrew  the  instrument  from  its  hold  upon  the  flange  of  the  coupling  by  means  of 
the  milled  edges  provided  for  this  purpose,  and  move  it  approximately  into  a  level 
plane,  then  again  screw  the  instrument  firmly  to  the  coupling  same  as  before. 
This  being  accomplished,  move  the  instrument  over  the  given  point  on  the  ground 
by  means  or  the  centering  arrangement  described  later  on,  and  level  up  carefully 
by  the  leveling  screws  alone.  It  will  be  seen  that  this  quick-leveling  attachment 
is  operated  entirely  independent  of  the  leveling  screws  or  centering  arrangement. 
Of  course,  when  this  device  is  to  be  used  for  several  days  in  succession,  it  is  not 
necessary  to  detach  it  from  the  tripod  every  time  the  instrument  is  to  be  removed. 
In  such  cases  the  instrument  only  should  be  detached  from  the  coupling.  When- 
ever it  becomes  desirable  to  detach  the  coupling  from  the  tripod,  it  can  best  be 
performed  by  allowing  the  instrument  to  remain  fastened  to  the  coupling,  then  by 
taking  hold  of  the  milled  edge  of  the  coupling  unscrew  in  the  usual  manner.  In 
cases  where  the  coupling  has  been  permanently  attached  to  a  tripod,  the  small 
screws  connecting  it  to  the  tripod  head  must  first  be  removed. 

To  secure  the  greatest  possible  stability  to  the  instrument,  the  outside  diameter 
of  the  hollow  hemisphere  is  equal  to  the  distance  between  the  leveling  screws  of 
the  instrument;  and  to  secure  a  smooth  and  ready  action,  leather  washers  are 
provided  in  the  socket  which  act  against  the  hemisphere.  However,  when  the 
instrument  is  clamped  to  the  flange  of  the  coupling  these  washers  recede,  and  the 
metal  surfaces  are  brought  into  direct  contact  with  each  other. 

The  Gradienter  Screw. 

This  very  convenient  attachment  consists  simply  in  a  screw  working  against 
the  clamping  arm  suspended  from  the  horizontal  axis,  and  on  the  opposite  side 
from  the  vertical  arc.  A  strong  spiral  spring  is  set  directly  opposite  the  screw, 
and  presses  the  clamp  arm  against  the  end  of  it.  This  screw  is  cut  with  great  care 
in  a  lathe.  It  has  a  large  silvered  head  graduated  into  fifty  equal  parts.  As  the 
screw  is  turned,  the  head  passes  over  a  small  silvered  scale,  so  graduated  that  one 
revolution  of  the  screw  corresponds  to  one  space  of  the  scale. 


46 

Obviously  then,  the  number  of  whole  revolutions  made  by  the  screw,  in  turning 
the  telescope  through  a  vertical  arc,  can  be  ascertained  from  this  scale.  The  clamp 
arm  of  the  telescope  has  its  clamping  screw  just  above  the  horizontal  axis,  in  the 
usual  manner.  When  this  screw  is  free,  the  telescope  may  be  revolved ;  but  when 
it  is  clamped,  the  telescope  can  only  be  moved  by  the  gradienter  screw,  which  thus 
takes  the  place  of  the  ordinary  vertical  tangent  screw.  The  screw  is  cut  with  such 
a  value  of  a  single  revolution,  as  to  cause  the  horizontal  cross-line  of  the  telescope 
to  move  over  a  space  of  jjg  of  a  foot,  placed  at  a  distance  of  100  feet,  when  the 
screw  is  turned  through  one  of  the  smallest  spaces  on  its  graduated  head ;  and 
since  there  are  fifty  such  spaces  on  the  head,  it  follows  that  one  revolution  of  the 
screw  is  equivalent  to  ^  of  a  foot,  at  a  distance  of  100  feet.  The  numbered  gradua- 
tions on  the  screw  head  are  then  each  equivalent  to  ^  of  a  foot  in  100  feet ;  and  two 
entire  revolutions  of  the  screw  would  be  twice  55,  or  1  foot  to  the  100.  It  is  readily 
seen  that  grades  can  be  established  with  great  rapidity  with  this  screw.  It  is  only 
necessary  after  setting  the  gradienter  screw  to  zero,  and  leveling  and  clamping  the 
telescope,  to  move  it  up  or  down  as  many  spaces  of  the  head  of  the  gradienter  screw 
as  there  are  hundredths  of  feet  to  the  hundred,  in  the  grade  to  be  established. 
Thus,  to  establish  a  grade  of  lft  85,  the  screw  head  is  turned  through  three  whole 
spaces  of  the  scale,  which  corresponds  to  l.ft  50,  and  through  three  of  the  numbered 
divisions,  and  five  of  the  shortest  ones  to  make  up  the  entire  reading  of  1."  85. 

For  measuring  distances  this  screw  takes  the  place  of  stadia  lines,  and  is  more 
convenient ;  since  for  any  approximately  horizontal  distance,  the  space  on  an  ordi- 
nary leveling  rod  expressed  in  hundredths  of  feet,  included  in  two  revolutions  of 
the  screw,  will  be  the  number  of  feet  the  level  rod  is  distant  from  the  center  of  the 
instrument.  Thus  the  difference  between  two  readings  of  the  level  rod  was  2" .  965 
when  the  telescope  was  moved  in  altitude  through  two  revolutions  of  the  screw. 
The  rod  therefore  was  distant  296.5  feet. 

It  is  unnecessary  even  that  a  leveling  rod  be  used.  A  ranging  pole  or  walking 
stick,  or  any  arbitrary  length  which  can  afterwards  be  measured,  will  suffice.  Thus 
a  stick,  which  was  afterwards  measured  and  found  to  be  3".  38  long,  was  found  to 
be  subtended  by  3^  revolutions  of  the  screw  at  an  unknown  distance. 

In  this  case  the  distance  was  — 

i||  X  100  =  213 .9  feet. 
1  •  58 

In  case,  however,  the  distance  to  be  measured  is  not  approximately  in  the  same 
level  plane  with  the  transit  telescope,  it  is  necessary  to  compute  the  distance,  from 
the  readings  of  the  rod.  In  taking  such  readings  at  an  altitude,  it  is  customary  to 
incline  the  rod  towards  the  telescope,  and  by  trial  find  the  least  space  subtended  by 
two  stadia  lines.  A  skilful  rod-man  will  plumb  a  rod  more  readily  than  he  can 
incline  it  at  the  proper  angle,  and  a  reading  of  the  plumb  rod  can  be  taken  with 
jrreater  accuracy,  and  in  less  time  than  with  the  inclined  rod ;  but  it  ordinarily 
involves  some  additional  computing  to  reduce  such  vertical  readings  to  horizontal 
<listances.  With  the  view  of  reducing  the  computation  to  a  simple  multiplication, 
the  following  table  is  appended  with  the  trignometrical  argument  on  which  it 
depends.  The  engineer  will  notice  the  solution  is  not  rigorously  exact,  but  is  suf- 
ficiently so  for  all  cases  in  practice. 


47 

In  the  above  figure, 

TH  =  the  transit  horizontal  sight  line. 
The  angle  HTB  =  the  angle  of  elevation  of  the  telescope  to  the  foot  of  the  rod 

=  E. 
"        "      BTA  =  the  angle  subtended   by  any  number  of  revolutions  of  the 

gradienter  screw  =  G. 
AB  =  the  length  of  the  rod  included  by  the  angle  G,  when  the  rod 

is  vertical  =  R. 
CB  is  drawn  perpendicular  to  TB. 

Then,  CBA  =  BTH=E        TAH  =  90°—  (E  +  G) 

J5=       (90°-  CE  +  G)  )      cog  E  cos  G  -  sin  E  sin  G. 
AB  sin  (90°4-  G)    :  ~~  cos  G. 

.-.  BC=R  (cos  E—  tan  G  sin  E.) 

tan  G=—  -  where  h  is  the  height  above  a  horizontal  line,  subtended  by 
one  revolution  of  the  gradienter  screw  at  a  distance  a. 
n  is  the  number  of  revolutions  made  in  any  given  case. 

BT  =  ^rBC  =  R4-(cosE  —  —  sinE) 

nh  nh  ^  a 


.-.BT  =  R          cos  E  —  sinE          ........      I. 

and 

HT=BT  cosE 

.-.HT=R       rCos'E—  ^sin2E        .......      II. 


Formulas  I  and  II  are  general  formulas  for  any  gradienter  screw.  In  C.  L. 
Berger  &  Sons'  transits  the  screw  is  cut  and  placed  so  that  when  a=  100,  for 
n  =2  and  A  =  i,  by  substitution  these  formulas  become, 

BT  =  R  (100  cos  E  —  sin  E.) 

HT  =  R  (100  cos  2E  —  y2  sin  2  E.) 

Where  BT  =  the  direct  distance  from  the  center  of  the  horizontal  axis  of  the 

transit  to  the  foot  of  the  vertical  rod. 

HT  =  the  horizontal  distance  from  the  center  of  the  horizontal  axis  of  the 

transit  to  the  plumb  line  dropped  from  the  foot  of  the  vertical  rod. 

R  =  the  space  included  on  the  vertical  rod  by  two  revolutions  of  the 

gradienter  screw. 

E  =  the  elevation  of  the  foot  of  the  rod  above  the  horizontal  sight  line 
of  the  telescope. 

When  the  angle  E  becomes  an  angle  of  depression  instead  of  elevation,  then  the 
point  B  is  the  upper  end  of  the  part  of  the  rod  used,  A  B.  The  distance  B  T  in 
this  case  is  the  direct  distance  between  the  center  of  the  horizontal  axis  of  the  tele- 
scope and  the  upper  reading  of  the  vertical  rod  in  the  valley. 

The  distance  H  T  is,  as  before,  the  horizontal  distance  between  the  center  of 
the  horizontal  axis  of  the  telescope,  and  the  plumb  line  prolonged  in  this  case 
upwards  from  the  upper  end  of  the  vertical  rod.  The  plumb  line  in  all  cases  coin- 
cides with  the  direction  of  the  rod. 

By  means  of  the  following  table,  it  is  only  necessary  to  multiply  the  factor 
opposite  the  angle  of  elevation,  by  the  space  included  upon  a  vertical  rod  by  two 
gradienter  screw  revolutions,  to  obtain  either  the  direct  or  horizontal  distance  of 
the  center  of  the  horizontal  axis  of  the  telescope  from  the  foot  of  the  rod  ;  or  the 
game  distance  from  the  upper  reading  of  the  vertical  rod  in  the  case  of  an  angle  of 
depression. 


48 


Gradienter  Screw  Table  I. 


Factors  to  be  multiplied  by  the  space  on  the  vertical  rod  expressed  in  feet  and  decimals, 
included  in  two  revolutions  of  the  gradienter  screw,  to  find  the  distance  of  the  foot 
of  the  rod  from  the  center  of  the  horizontal  axis  of  the  transit  telescope, 


Angle  of 
Elevation 

Factor  for  the 
Direct  Distance 
joo  cos  E-  sin  E) 

Factor  for  the 
Horizontal  Dist. 
(IOQCOS  2E—  1/» 
sinaE) 

Angle  of 
Elevation 
£. 

Factor  for  the 
Direct  Distance, 
loo  cos  E-  sin  E) 

Factor  for  the 
horizontal  Dist. 
IDC  cos*  F  —  Vi 
sin  a  E) 

o         / 

o          / 

0 

100.00 

IOO.OO 

15 

96-33 

93-<>5 

I 

99.96 

99-94 

i5    3° 

96.09 

92-59 

2 

99.90 

99.84 

16 

95.85 

92.14 

3 

99.8r 

99.67 

16    30 

95-6o 

91.66 

4 

99.69 

99-45 

17 

95-34 

91.17 

5 

99-53 

'    99-'5 

17    30 

95.07 

90.66 

6 

99-34 

98.80 

18 

94.80 

90.17 

7 

99-'3 

98-39 

18    30 

94-51 

89.63 

8 

98.89 

97-93 

J9 

94.22 

89.09 

9 

98.61 

97.41 

19    30 

93-93 

88.54 

10 

98.31 

96.81 

20 

93'63 

87.98 

10    30 

98.15 

96.51 

20      30 

93.32 

87.41 

ii 

97-97 

96.17 

21 

93.00 

86.83 

ii     30 

97-79 

95.82 

21       30 

92.67 

86.22 

12 

97.60 

95-47 

22 

92-34 

85.62 

12      30 

97.41 

95.11 

22      30 

92.01 

85.01 

'3 

97.21 

94-73 

23 

91.66 

84.37 

13    30 

97.01 

94-33 

23    3° 

9'-3' 

83.75 

H 

96.79 

93.92 

24 

90.94 

83.08 

H    30 

96-56 

93-48 

24    30 

90.59 

8243 

'5 

96-33 

93-°5 

25     oo 

90.21 

81.76 

49 

In  practically  applying  this  table,  it  is  preferable  to  take  the  mean  of  several 
readings  of  the  rod  in  each  position  of  the  gradienter  screw.* 

Thus,  with  the  target  near  the  foot  of  the  rod,  and  then  moved  to  correspond  to 
two  revolutions  of  the  gradienter  screw,  three  readings  hi  each  position  were  a« 
follows : 

I.  II. 

Altitude   18°  2V 

ft 

0.625 
0.627 
0.625 

Means,  .     .     .    0.626  3.378 

0.626 


Difference, 2.752 

Factor  for  direct  distance  for  18°     =  94.80        For  Horizontal  Distance  =  90.17 
"  "    1S°30'=  94.51          "  "  "        =89.63 


Differences,    .     .     .  =0.29  0.54 

Therefore,  the  factor,  for  18°  20'  will  be  for  the  direct  distance  94.80,— ?3  of  0.28 
-a  94.61,  and  for  the  horizontal  distance,  90.17  —  2/3  of  0.54  =  89.81. 

Then  we  have,  2.752  X  94.01  =        260.37  =  the  direct  distance. 

2.752  X  89.81  =        247.15  =  the  horizontal  distance. 

This  direct  distance  being  the  distance  from  the  position  of  the  foot  of  the  rod 
or  the  lower  target  to  the  center  of  the  horizontal  axis  of  the  telescope,!  and  the 
horizontal  distance,  the  one  usually  desired,  that  distance  reduced  to  a  level  line. 

The  mean  value  of  two  revolutions  of  the  Gradienter  Screw  in  arc.  is  34'  23*. 
Hence  the  value  in  arc  of  one  of  its  smallest  divisions  on  the  head  is  20"  nearly. 
Vertical  angles  therefore  may  be  laid  off  with  facility  when  they  are  confined  to 
the  range  ot'  the  screw. 

•To  insure  at  all  times  accurate  results,  the  telescope  axis  should  revolve  free,  but  without  any  looseness  in 
the  bearings.  The  engineer  should  examine  these  bearings  from  time  to  time,  and,  if  necessary,  fresh  and  pure 
watch  oil  must  be  applied. 

To  make  a  measurement  with  a  micrometer  screw,  its  graduated  head  should  be  set  back  slightly,  then  bring 
it  up  to  the  readings  in  the  same  direction  in  which  the  measurement  must  be  effected. 

*  Should  the  engineer  desire  the  direct  distance  between  the  foot  of  the  rod,  and  tk*  Joint  *vrr  mkick  t*t 
tivmb-iob  is  suspended,  it  may  be  found  by  the  following  formula. 


X  =  V  </a  "I-/2  +  'Ifd  sin  E. 
or  putting  it  in  a  shape  adapted  for  logarithmic  computation, 


Where       x  =  the  distance  from  the  point  under  the  plumb-bob  to  the  foot  of  the  vertical  rod. 
</=the  direct  distance  obtained  as  above. 

/  =  the  distance  from  the  center  of  the  horizontal  axis  is  to  the  point  under  th«  plumb-bob. 
f  <=  the  angle  of  elevation  of  the  foot  of  the  rod,  as  above. 


50 


The  subjoined  table  affords  a  ready  means  of  expressing  any  number  of  reroln- 
tions,  and  parts  of  a  revolution,  in  arc ;  and  the  converse,  of  degrees,  minutes  an<? 
seconds,  in  revolutions  of  the  screw : 

Gradienter  Screw  Table  II. 


To  convert  a  reading  of  the  Screw 
into  Arc, 

To  convert  Arc  into  a  reading  of 
the  Screw. 

Gradienter 
Screw. 

Arc. 

Gradienter 
Screw. 

Arc. 

Arc. 

Gradienter 
Screw. 

Arc. 

Gradienter 
Screw. 

RCY.    Div. 

0        f           If 

Rev.    Div. 

o      f       ir 

o       f       rr 

Rev.      Div. 

0        f            If 

Rev.      Div. 

0      0 

O  O      O 

2      0 

o  34  25 

O       O       O 

0        O.O 

o     8  oo 

0    23.5 

0       I 

0    2O 

o 

o  5i  35 

0      0    10 

o      0.5 

o     8  30 

o  25.0 

0       2 

o  40 

4    ° 

i     8  45 

0      0    20 

0        1.0 

o     9  oo 

o  26.0 

d 

1       0 

5    ° 

i  25  55 

o     o  30 

o      1.5 

o    9  30 

o  27.5 

o    4 

1  25 

6    o 

i  43  10 

o    o  40 

O        2.O 

O    IO  OO 

o  29.0 

0    5 

i  45 

7    ° 

2      O    2O 

o    o  50 

o      2.5  ' 

0    20    00 

i     8.0 

o    6 

2     5 

8    o 

2  17  35 

0       I    OO 

o     3.0 

o  30  oo 

i  37.0 

o    7 

2    25 

9    o 

2  34  45 

o     i  30 

0     4-5 

o  40  oo 

2    19.0 

o    8 

2  45 

10     0 

2   52      O 

0      2    00 

o     6.0 

o  50  oo 

2  55-5 

o    9 

3    5 

II      O 

3    9  10 

0       2    30 

o    7-5 

I    OO    OO 

3  24-5 

O    IO 

3  25 

12      O 

3  26  20 

o     3  oo 

o     9.0 

2   00  00 

6  49.0 

0   2O 

6  50 

13    o 

3  43  30 

033° 

o    10,5 

3  oo  oo 

10  23.5 

o  30 

IO   2O 

14    o 

4    o  45 

o    4  oo 

0     12.0 

4  oo  oo 

13  48.0 

o  40 

*3  45 

15    o 

4  i7  55 

043° 

0    13-5 

5  oo  oo 

17  22.5 

I       0 

17  jo 

o    5  oo 

o    15.0 

I    IO 

20  40 

053° 

o    16.0 

I  20 

24  05 

o     6  oo 

0  '7-5 

1  30 

27  3° 

o    6  30 

o   19.0 

I  40 

3°  55 

o     7  oo 

o    20.5 

2      0 

34  25 

o    7  30 

O     22.  0 

51 

Thus,  the  telescope  being  leveled,  the  gradienter  screw  was  turned  through  a 
space  of  11"T'  23dm  required  the  arc : 

11  revolutions,  =  3°    9'  10" 

20  divisions,      =0     6     50 

3  =010 


The  whole  arc,     .     .     .    =3°  17'   00" 
Conversely,  it  was  desired  to  turn  off  a  vertical  angle  of  4°  35" 

Then  we  have  — 

4°    0'    0"  =  13'"-  48diT-.0 

30     0  =  1  37     .0 

50=  15    .0 

40  =  2    .0 


The  space  on  the  head  of  the  screw  =  16rev-     2diT-  .0 

The  engineer  will  bear  in  mind  that  the  examples  given  are  purposely  given  in 
detail :  that  in  practice  the  operations  may  be  mental  ones. 

It  will  be  seen  that  the  vertical  gradienter  can  be  used  for  a  variety  of  purposes ; 
measuring  distances,  grades,  differences  of  levels,  vertical  angles,  and  is  a  useful 
check  against  errors  of  rod  or  chain  measurement. 

Messrs.  C.  L.  Berger  &  Sons  have  also  applied  the  same  principle  to  their  hori- 
zontal tangent  screws.  By  graduating  a  silver  head  attached  to  these  screws  sub- 
divisions ot  one  minute  of  arc  are  readily  made. 

For  constant  use  with  these  screws  it  is  better  to  have  a  rod  with  two  inovafclt 
targets,  or  a  rod  painted  with  white  and  black  squares  as  used  in  the  coast  survey. 


Stadia  Lines 

The  gradienter  screw  is  so  universal  in  its  application  and  can  be  so  readily  used 
for  angular,  distance  or  grade  measures,  that  it  will  generally  be  found  best  to  have 
it  upon  transits  designed  for  current  work.  There  are  some  cases  however  where 
stadia  lines  are  more  expeditious  in  use  than  the  gradienter  screw,  and  give  quite 
as  exact  results. 

Stadia  lines,  for  instance,  where  an  instrument  is  to  be  used  for  distance  measures 
alone,  commend  themselves  for  their  greater  simplicity.  For  such  work,  non-adjust- 
able lines,  in  connection  with  an  inverting  eye-piece,  give  the  best  results.  If  the 
lines  are  adjustable,  in  the  field  usage  of  an  instrument  they  may  alter  their  distance 
apart ;  and  there  is  a  rapidity  of  work  with  fixed  lines,  and  a  rod  graduated  for 
telemetrical  work,  which  is  not  reached  in  any  other  way. 

These  lines  may  be  webs,  or  platinum,  or  they  may  be  ruled  on  glass.  The  lat- 
ter are  extremely  accurate,  but  the  use  of  them  is  necessarily  limited  in  the  tele- 
scopes of  field  instruments  for  the  following  reasons  :  thin  as  the  glass  may  be  on 
which  the  lines  are  ruled,  and  intercepting  only  a  small  amount  of  light,  yet  the  film 
of  dampness  and  dirt  soon  collecting  on  it  will  intercept  a  great  amount  of  light 
which  in  time  may  become  a  very  serious  impediment  in  the  use  of  the  telescope. 
Another  objection  to  their  general  adoption  consists  in  the  fact  that  as  the  image 
of  an  object  is  focussed  in  the  plane  of  these  glass-lines,  a  portion  of  the  light  of  the 
image  will  become  reflected  from  the  polished  surfaces  of  this  glass,  causing  at 
times  a  disturbance  in  the  clearness  of  vision.  Besides,  this  glass-"  micrometer," 
as  placed  in  most  telescopes,  is  very  difficult  of  access  and  must  needs  be  removed 
for  cleaning,  thereby  increasing  the  liability  of  becoming  broken,  or  detached  from 
its  mounting. 


Section 
showing  the 
Diaphragm 
natural  Size. 


52 

Plumbing  and  Centering  Arrangements. 

It  now  remains  to  speak  of  several  conveniences  of  the  instrument  under  con- 
gideration.  By  a  simple  mechanical  contrivance  the  plumb-bob  when  suspended 
from  the  instrument  can  be  set  immediately  at  any  desired  height.  It  is  suspended 
directly  from  the  center  of  the  instrument,  and  not  from  the  tripod  head.  This 
precaution  shou1'1  be  taken  T«r>th  every  instrument,  since  otherwise,  when  there  is 
difficulty  in  setting  up  an  instrument,  and  the  legs  are  unsymmetrically  placed,  the 
plumb-line  will  not  pass  through  the  center  of  the  instrument. 

The  instrument  is  provided  with  the  shifting  tripod,  better  known  as  the  shifting 
center,  by  means  of  which,  when  the  plumb-bob  of  the  instrument  is  within  a  fraction 
of  an  inch  over  a  point  on  the  ground,  it  may  be  brought  immediately  over  it,  by 
moving  the  body  of  the  instrument  on  its  lower  level  plate.  This  is  probably  the 
greatest  time-saving  arrangement  which  modern  makers  have  introduced  in  engin- 
eers' transits. 


Shifting-  Center  for  a  Transit  with  Three  Leveling1  Screws. 

There  are  several  methods  of  placing  a  level  or  transit  with  three  leveling  screws 
upon  the  tripod  head.  One  is  the  tribrach  style  where  the  leveling  screws  rest  in  ra- 
dial grooves  in  a  triangular  shaped  foot-plate  which  screws  on  to  the  tripod.  This 
method  is  used  extensively  in  Europe,  but,  as  the  instrument  rests  only  by  its 
own  weight  in  these  grooves  it  is  liable  to  changes  in  position  during  use  and  this  in- 
stability becomes  greatly  aggravated  when  the  leveling  screws  become  worn. 

Another  method  in  transits  is  to  rest  the  leveling  screws,  provided  with  small  bearing 
cups  or  washers  at  their  lower  ends,  directly  upon  the  smooth  top  surface  of  the  tripod 
head  to  allow  centering  of  the  instrument  over  a  given  point.  The  pressure  of  a  spiral 
spring  forming  part  of  the  instrument  fastener  is  then  applied  to  fix  the  position  of 
instrument  on  the  tripod  head. 

This  latter  method  of  connecting  a  transit  to  a  tripod  is  very  insecure,  inasmuch  as 
the  slightest  change  in  the  position  of  the  instrument,  while  reading  a  series  of  angles, 
will  greatly  affect  the  results. 

Thus  it  is  seen  that  a  transit  lacking 
the  necessary  stability  on  its  tripod 
often  proves  almost  useless  in  the 
finer  field-work. 

Messrs  C.  L.  Berger  &  Sons  make 
the  leveling  screws  to  rest  in  radial 
grooves  in  a  separate  piece  made  to 
slide  on  the  tripod  head  as  shown  in 
cut.  A  clamp-nut,  provided  with  a 
large  flange  and  handles,  serves  to 
secure  this  sliding  piece  to  the  tripod 
in  any  position  in  the  range  of  its 
lateral  motion.  The  instrument  fas- 
tener, being  part  of  the  tripod  proper, 
has  a  large  cylindrical  hole  in  the 
threaded  stem  to  allow  the  hook  and 
chain,  suspended  directly  from  the 
transit  center,  to  pass  through  and 
to  swing  freely  in  every  direction,  so 
that  when  the  plumb-bob  is  attached 
its  point  will  be  truly  in  the  continu- 
ation of  the  vertical  center  of  the 
instrument.  The  milled  head  at  the 
lower  end  of  the  fastener  serves  to 
screw  the  latter  to  the  instrument, 
andamilledheaded  nut  acting  against 
a  spiral  spring  secures  the  instrument 
to  the  tripod.  In  use,  the  pressure 
of  this  spring  must  be  sufficient  to 
take  up  the  back  lash  or  any  loose- 


53 

ness  that  may  exist  in  the  leveling  screws;  but  to  secure  the  necessary  stability  of  the 
instrument  to  the  tripod,  the  clamp-nut  should  be  well  fastened  to  the  sliding  piece. 
To  operate  the  shifting  center,  both  the  spiral-spring  and  the  clamp-nut  must  be  re- 
leas?d  slightly  from  their  hold  upon  the  tripod  and  the  sliding  piece,  when  the  instru- 
ment can  be  moved  over  the  given  point  on  the  ground.  This  device  adds  about  2  Ibs. 
to  the  weight  of  the  tripod. 

Arrangement  for  Offsetting  at  Bight  Angles. 

The  most  common  off-set  with  the  transit  is  one  at  90°  to  the  line  of  sight. 
Several  methods  have  been  proposed  for  doing  this  without  disturbing  the  telescope. 

Messrs.  C.  L.  Berger  &  Sons  have  a  very  neat  one ;  it  consists  in  simply  per- 
forating the  horizontal  axis,  so  that  by  drawing  the  head  back  fifteen  or  twenty 
inches  from  one  end  of  the  axis,  the  eye  may  be  placed  so  that  the  eye,  the  hori- 
zontal axis  of  the  telescope,  and  a  rod  set  beyond,  may  be  readily  placed  in  the 
same  straight  line,  at  right  angles  to  the  line  of  sight  of  the  telescope,  no  matter 
at  what  altitude  the  telescope  may  be  pointing. 

In  off-setting  by  the  arrangement  proposed  above,  the  rod  is  made  plumb  by 
lining  it  with  the  plumb-line  ot  the  instrument  itself.  The  advantage  of  this  method 
is,  that  it  holds  equally  well  for  any  inclination  of  the  telescope.  The  disadvantage 
is,  that  the  engineer  is  obliged  to  leave  the  eye-end  of.  the  telescope  at  each  off-set 
made 


Setting  Up. 

In  setting  up  a  transit,  push  the  iron  shoe  of  one  leg  firmly  into  the  ground,  by 
pressing  on  the  other  two  legs  near  the  tripod  head.  Having  secured  a  firm  found- 
ation for  this  leg,  separate  the  other  two  legs,  at  the  same  time  drawing  the  tripod 
head  toward  you.  Then  set  the  two  remaining  legs  in  the  same  manner  as  the  first 
one.  If  the  ground  is  pretty  level,  merely  noticing  that  the  tripod  feet  are  equi- 
distant, r  ill  insure  that  no  unsightly  appearance  will  be  ^iven  to  the  leveling  screws. 
If  the  ground  is  uneven,  however,  nothing  but  practice  can  produce  a  graceful 
position  of  the  instrument.  The  plumb-bob  attached  to  the  instrument  should 
swing  within  say  half  an  inch  of  the  point  on  the  ground,  and  the  plate  on  which  the 
leveling  screws  rest,  if  possible,  should  be  approximately  horizontal,  when  this 
stage  is  completed. 

Now  with  the  level  screws  not  tightened  up,  after  leveling  approximately, 
bring  the  plumb-bob  exactly  over  the  point  on  the  ground,  by  moving  the  body  of 
the  instrument  on  its  shifting  head.  Then  complete  the  leveling  of  the  instrument, 
and  it  is  ready  for  work. 

The  Adjusting  of  the  Transit 

If  the  instrument  is  out  of  adjustment  generally,  the  engineer  will  find  it  profit- 
able to  follow  the  makers  in  not  completing  each  single  adjustment  at  once,  but 
rather  bring  the  whole  instrument  to  a  nice  adjustment  by  repeating  the  whole 
series. 

After  setting  up,  bring  the  two  small  levels  each  parallel  to  a  line  joining  two 
of  the  opposing  leveling  screws.  Bring  both  bubbles  to  the  center  of  the  level  tubes, 
by  means  of  the  leveling  screws.  In  doing  this,  place  the  two  thumbs  on  the  inner 
edges  of  the  two  leveling  screws,  parallel  to  the  bubbles,  and  the  fore  fingers  ot 
each  hand  on  the  outer  edge.  Turn  the  leveling  screws  so  that  both  thumbs  move 
inwards  or  both  outwards.  In  the  former  case  the  bubble  will  move  toward  the 
right,  in  the  latter  case  toward  the  left. 

Now  turn  the  instrument  180°  hi  azimuth.  If  the  small  levels  still  hare  their 
bubbles  in  the  center  of  their  tubes,  these  levels  are  adjusted,  and  the  circles  are 
respectively  as  nearly  horizontal  and  vertical  as  the  maker  intended  them  to  be. 

If  the  bubbles,  however,  are  not  in  the  center  of  their  tubes,  then  bring  «hem 
half  way  back  by  means  of  the  leveling  screws,  and  the  remaining  half  by  means 
of  the  adjusting  screw  at  the  end  of  each  of  the  level  tubes. 

It  may  be  necessary  to  repeat  this  adjustment  several  times,  but  when  made,  the 
instrument  once  leveled  will  have  its  small  levels  in  the  center  of  their  tubes  through 
an  entire  rotation  of  the  circle. 


54 

To  make  the  adjustment  for  Parallax.  This  adjustment  common  to  all  tele- 
scopes used  in  surveying  instruments  is  that  of  bringing  the  cross  hairs  to  a  sharp 
focus,  at  the  same  time  with  the  object  under  examination.  Point  the  telescope  to  the 
sky,  and  turn  the  eye-piece  until  the  cross  hairs  are  sharp  and  distinct.  Since  the 
eye  itself  may  have  slightly  accommodated  itself  to  the  eye-piece,  test  the  adjustment 
by  looking  with  the  unaided  eye  at  some  distant  point,  and  while  still  looking,  bring 
the  eye-piece  of  the  telescope  before  the  eye.  If  the  cross  hairs  are  sharp  at  the 
first  glance,  the  adjustment  is  made.  Now  focus  in  the  usual  manner  upon  any 
object,  bringing  the  cross  hairs  and  image  to  a  sharp  focus  by  the  rack- work  alone. 
A  point  should  remain  bi-sected  when  the  eye  is  moved  from  one  side  of  the  eye- 
piece to  the  other. 

To  make  the  vertical  cross-line  perpendicular  to  the  plane  of  the  hori- 
zontal axis,  simply  bi-sect  some  point  at  the  lower  edge 'of  the  field  of  view  of  the 
telescope  by  means  of  the  tangent  screw  and  note  whether-  it  continues  bi-sected  by 
this  cross-line  throughout  its  entire  length  when  the  telescope  is  moved  in  altitude.  If 
it  does  not,  and  the  point  is  to  the  right  of  the  line  in  the  upper  part  of  the  field,  the 
adjustment  is  made  by  loosening  the  four  capstan -headed  screws,  and  rotating  the 
reticule  in  the  direction  of  a  left-handed  screw,  until  the  point  remains  bi-sected  and 
then  tighten  all  four  adjusting  screws.  Again,  bi-sect  the  point  by  means  of  the  tan- 
gent screw.  It  should  now  remain  bi-sected  throughout  the  length  of  the  cross-line,  if 
not,  this  operation  must  be  repeated. 

To  adjust  the  horizontal  wire  proceed  as  follows:  In  transits  of  our  make 
which  have  erecting  eye-pieces  the  mechanical  construction  of  the  telescope  is  so 
perfect  that  the  horizontal  wire  may  be  placed  in  the  optical  axis  by  simply  placing  it 
in  the  center  of  the  field  of  view  by  the  adjusting  screws.  See  diagrams  on  page  58. 
However,  in  telescopes  having  inverting  eye-pieces  the  horizontal  wire  can  be  placed 
in  the  optical  axis  only  by  rotating  the  telescope  in  improvised  wyes. 

To  adjust  the  vertical  wire  which  in  the  transit  is  the  most  important.  When 
that  is  to  be  alone  adjusted  in  the  field,  it  is  usually  done  according  to  the  following 
simple  directions:  Level  up  the  instrument  approximately  and  select  two  distant  points 
in  opposite  directions  from  the  instrument,  preferably  in  the  same  horizontal  plane,  such 
that  the  vertical  cross-line  will  bi-sect  them  both  when  the  telescope  is  pointed  upon 
one,  and  then  the  telescope  is  reversed  on  its  horizontal  axis.  After  bi-secting  the 
second  point  selected,  revolve  the  instrument  in  azimuth  and  bi-sect  the  first  point 
again  by  means  of  the  tangent  screw.  Reverse  the  telescope  on  its  horizontal  axis 
again,  and  if  the  second  point  is  now  bi-sected  the  adjustment  for  collimation  of  the 
vertical  wire  is  correct.  If  it  is  not  bi-sected,  move*  the  vertical  wire  one-fourth  of 
the  distance  between  its  present  position  and  the  point  previously  bi-sected. 
Again  bi-sect  the  first  point  selected,  reverse  the  telescope  and  find  a  new  point  pre- 
cisely in  the  new  line  of  sight  of  the  telescope;  these  two  points  will  now  remain 
bi-sected  when  the  instrument  is  pointed  upon  them  in  the  manner  described  above,  if 
the  adjustment  is  correctly  made.  If  the  two  points  are  not  now  both  bi-sected,  the 
adjustment  must  be  repeated  until  this  be  the  case. 

To  determine  whether  the  standards  are  of  the  same  height,  suspend  a 
plumb-bob  by  means  of  a  long  cord  from  a  height  say  of  from  thirty  to  forty  feet.  The 
plumb-bob  may  swing  in  a  bucket  of  water  to  keep  it  steady.  (Instead  of  a  plumb- 
line  the  reflection  of  a  church  spire  or  edge  of  a  tall  building  or  any  other  convenient 
object  may  be  viewed  in  a  bucket  of  water.)  Level  the  instrument  carefully,  and  point 
upon  the  plumb-line  at  its  base.  If  the  plumb-line  remains  bi-sected  throughout 
its  entire  length  when  the  telescope  is  moved  in  altitude,  and  then  the  telescope  reversed 
and  again  made  to  bi-sect  the  line  throughout  its  length  from  its  base  upward,  the  ad- 
justment is  correct.  Otherwise  make  the  adjustment  by  means  of  the  capstan-headed 
screw  directly  under  one  of  the  telescope  wyes.  Loosen  the  screws  in  the  pivot  caps 
and  turn  the  vertical  adjusting  screw  right  handed  to  raise  the  wye  bearing  one 
quarter  of  the  error  to  be  corrected.  If  the  telescope's  axis  is  already  too  high,  the 
vertical  adjusting  screw  should  be  loosened  a  little  more  than  needed  and  then  by  the 
screws  of  the  pivot  cap  the  wye  bearing  should  be  lowered  until  it  just  touches  the  ver- 
tical adjusting  screw.  The  screws  of  the  pivot  cap  must  now  again  be  loosened  and  the 
wye  bearing  raised  by  a  right  hand  turn  of  the  vertical  adjusting  screw,  as  explained 
above,  until  the  telescope's  axis  is  in  the  correct  position.  If  this  is  not  done  the  ad- 
justable bearing  is  likely  to  stick  and  not  rest  on  the  adjusting  screw,  thus  causing 
liability  to  derangement.  The  screws  in  the  pivot  cap  should  then  be  turned  down 
just  enough  to  prevent  looseness  in  the  bearings. 

When  there  are  opposing  nuts  in  place  of  the  vertical  adjusting  screw  as  is  the 
case  in  almost  all  of  our  transits  to  secure  a  more  ready,  positive  and  above  all  a  last- 
ing adjustment  —  then  while  the  modus  operandi  remains  the  same,  the  action  of  the 
adjusting  nuts  to  raise  or  lower  the  wye  bearings  is  just  opposite  from  that  described 
above. 


55 

Instead  of  using  a  plumb-line  a  simpler  method  having  the  advantage  of  not  re- 
quiring the  instrument  to  be  leveled  up  carefully  is  as  follows:  Set  up  the  instrument 
as  near  as  may  be  convenient  to  a  building,  say  about  20  feet,  in  order  to  get  as  high  an 
altitude  as  possible.  Level  up  only  approximately,  clamp  and  bi-sect  a  point  at  the 
base  by  the  tangent  screw.  Then  elevate  the  telescope  and  find  a  well-defined  object 
as  high  as  possible,  only  using  the  telescope's  horizontal  axis.  Now  reverse  telescope 
and  move  instrument  on  its  vertical  center,  again  clamp,  and  bi-sect  the  point  at  the 
base.  If  when  the  telescope  is  elevated  it  bi-sects  the  high  object  selected  the  adjust- 
ment is  correct.  If  it  does  not,  proceed  as  described  in  the  above  method. 

To  adjust  the  level  to  the  line  of  col  Munition  of  the  horizontal  wire  one 
method  is  to  use  a  sheet  of  water,  or  where  that  is  not  available,  two  stakes  which  are 
driven  with  their  surfaces  in  the  same  level  plane.* 

To  make  the  adjustment  with  the  stakes,  level  up  the  transit  half  way 
between  two  points  lying  very  nearly  in  a  horizontal  line,  and  say  300  feet  apart. 
Drive  a  stake  at  one  of  these  points,  place  the  rod  on  it  and  take  a  reading,  first  bring- 
ing the  bubble  to  the  middle  of  its  tube.  Point  the  telescope  in  the  opposite  direction, 
again  bring  the  bubble  to  the  middle  of  its  tube,  and  drive  a  second  stake  at  the  second 
point  selected  until  the  rod  held  upon  the  second  stake  gives  the  same  reading  as  when 
held  upon  the  first  stake.  The  tops  of  these  two  stakes  now  lie  in  the  same  level  line. 
Take  up  the  transit  and  set  it  outside  in  line,  as  near  as  it  can  be  focussed  on  the 
first  stake  and  level  up.  Now  read  the  rod  upon  the  first  stake  with  the  bubble  in  the 
center  and  then  upon  the  second.  If  the  two  readings  agree,  and  the  bubble  is  in  the 
middle  of  its  tube,  the  adjustment  is  correct.  If  the  two  readings  do  not  agree,  then  by 
means  of  the  telescope's  tangent  screw  elevate  or  depress  the  telescope  the  amount  re- 
quired until  the  horizontal  wire  reads  the  same  on  the  distant  rod.  Next  ref ocus 
on  the  near  rod,  take  a  reading,  then  focus  on  the  distant  rod  and  see  if  the  readings 
are  the  same,  if  not,  by  means  of  the  tangent  screw  again  make  the  horizontal  wire 
read  the  same  as  on  the  near  rod.  Repeat  this  operation  until  both  rods  read 
the  same.  Now  with  the  horizontal  wire  bi-secting  the  distant  reading  make  the  ad- 
justment of  the  level  by  its  capstan -headed  nuts  until  the  bubble  is  in  the  middle  of  its 
tube  when  the  level  will  be  parallel  to  the  line  of  collimation. 

Another  method  of  adjusting  the  attached  level  to  the  Transit  Telescope 
will  be  found  on  page  63. 

To  adjust  the  verniers  of  the  vertical  arc  or  full  circle  to  read  zero,  in  our 
Engineer's  Transit  having  the  vernier  between  the  legs  of  the  standard.  First  level 
up  the  instrument  carefully  so  that  the  telescope's  bubble  will  remain  in  the  middle 
of  its  tube  when  turned  180°  in  azimuth.  Then  set  the  zero  of  the  vernier  to  read 
within  about  %  minute  right  with  zero  of  the  vertical  arc.  Then  by  the  vertical 
tangent  screw  place  both  zeros  in  coincidence  and  examine  the  30'  lines  and  if  short 
the  vernier  must  be  moved  inwardly  so  that  both  of  the  end  lines  in  the  double  vernier 
will  read  right.  If  too  long  the  vernier  must  be  moved  outwardly  until  this  is 
attained ;  then  fasten  tightly.  Now  unloosen  only  just  enough  the  screws  that  hold 
the  vertical  arc  or  circle  to  the  horizontal  axis,  to  permit  of  "a  slight  shift,  and  then 
with  the  bubble  in  the  center  slightly  tap  one  of  the  spokes  of  the  arc  with  the  handle 
of  the  screw-driver,  until  the  zero  of  the  vernier  and  that  of  the  vertical  arc  are  in 
coincidence.  This  accomplished  now  fasten  the  vertical  arc  tightly  to  its  flange. 
Again  level  up  the  telescope  as  described  above  and  see  if  the  adjustment  is  correct;  if 
not,  again  slightly  unloosen  the  vertical  arc,  tap  it  into  position,  repeat  the  same  opera- 
tion over  again  until  it  is  correct. 

NOTE.  — If  the  vernier  for  the  vertical  arc  is  single,  made  to  read  both  ways,  in 
reading  it  proceed  to  the  right  or  left  on  the  upper  line  of  figures  in  the  direction  of 
the  graduation  used,  and  if  the  coincident  line  of  the  vernier  is  beyond  the  15'  line, 
continue  on  the  lower  line  of  figures  on  the  other  half  of  the  vernier,  so  that  the  whole 
graduation  from  0'  to  30'  lies  in  the  same  direction.  The  verniers  of  our  vertical  arcs 
are  however,  made  mostly  double  as  described  on  page  37. 

The  Adjustments  of  the  Full  Vertical  Circle  with  Double  Op- 
posite Verniers. 

When  the  vertical  circle  in  the  Engineers'  Transit  is  provided  with  a 
vernier  at  eye-end  or  with  double  opposite  verniers,  the  adjustment  of  the 
vernier  zero  for  normal  position  should  be  made  by  the  two  opposing  capstan-headed 
screws  attached  to  the  vernier  frame  at  side  of  standard.  Then  to  be  lasting  and 
to  avoid  any  strain  upon  the  frame  and  lugs  carrying  these  adjusting  screws,  pro- 
ceed as  follows  :  —  First  level  up  the  instrument  so  that  the  bubble  of  the  telescope 
and  plate  levels  remain  in  the  center  of  their  tubes  when  vernier  plate  is  turned  180° 
in  azimuth;  then  the  zero  of  vernier  "A,"  at  eye-end,  should  be  adjusted  by  the 

*In  general  practice  one  will  locate  the  stakes  permanently  at  some  convenient  place  near  the 


56 

capstan-headed  screw  at  left  to  read  zero  with  the  circle,  by  first  releasing  the  opposing 
screw  at  right  —  which  is  now  provided  with  a  milled  head  —  and  then  with  the  finger 
slightly  pressing  the  vernier  frame  against  the  left  hand  capstan-headed  screw,  turn  the 
latter  until  vernier  "A"  reads  zero.  Then  carefully  turn  the  milled  headed  opposing 
screw  at  right  towards  the  stud  until  it  barely  touches.  It  is  best  to  leave  even  a 
little  looseness  between  the  stud  and  opposing  screw  rather  than  to  have 
the  least  strain.  (Such  minute  looseness  can  be  easily  felt  by  the  finpers  but  it 
should  never  affect  the  readings  if  the  looseness  is  not  excessive.)  In  following 
this  method  we  reiterate,  that  the  above  adjustment  will  keep  for  years  and 
there  being  no  strain  between  the  opposing  screws  and  stud,  the  telescope's 
axis  will  always  revolve  with  perfect  freedom  in  the  wyes,  nor  will  there  be 
any  danger  to  warp  or  fracture  the  frame. 

If  the  telescope  is  reversible  over  the  bearings  as  in  the  Transit  Theodolite, 
then  the  vernier  frame  requires  a  reversible  tangent  screw  in  place  of  the  opposing 
adjusting  screws  just  explained  above.  Then  before  a  vertical  angle  can  be  taken, 
the  adjustment  of  the  vernier  zeros  for  position  must  first  be  made  by  the  vernier 
frame's  tangent  screw  when  the  telescope's  level  bubble  is  in  the  center  of  its  gradua- 
tion. In  this  latter  case  it  is  not  always  necessary  to  carefully  level  up  the  whole 
instrument. 

If  a  vertical  circle  has  a  level  attached  to  its  vernier  frame  as  in  most  Tran- 
sit Theodolites  then  the  adjustment  of  this  level  and  verniers  for  position  must  be 
made  in  the  following  manner: 

Place  the  telescope  in  the  horizontal  plane  by  means  of  its  tangent  screw,  then 
move  the  vernier  frame's  tangent  screw  until  the  zero  line  of  the  double  verniers, 
marked  A,  is  in  coincidence  with  the  zero  line  of  the  vertical  circle,  arid  now  raise  or 
lower  the  adjusting  screw  of  this  level,  as  the  case  may  be,  until  the  bubble  is  in  the 
centre  of  its  tube. 

It  is  now  supposed  that  the  zero  line  of  the  double  opposite  verniers,  marked  B,  is 
also  in  coincidence  with  that  of  the  vertical  circle.  If  not,  the  verniers  marked  B,  can 
be  moved  after  releasing  the  capstan-headed  screws,  until  both  zero  lines  on  that  side 
of  the  vertical  circle  are  also  in  coincidence.  However,  this  is  a  very  laborious  pro- 
ceeding for  those  uninitiated  in  this  work,  and  as  it  cannot  always  be  made  quite  exact, 
owing  to  the  mode  of  mounting  the  vertical  circle  on  the  telescope's  axis,  it  will  be  found 
easiest  to  eliminate  errors  of  excentricity  in  the  graduation  of  the  vertical  circle  and 
verniers  by  reversing  the  telescope  and  taking  the  mean  of  the  readings.  The  vertical 
circle  is  generally  graduated  from  0°  to  90°  and  back,  and  the  verniers  are  double, 
so  that  angles  of  elevation  and  depression  can  be  read  with  ease  and  dispatch. 


The  striding  Level  resting  on  special  collars  between  the 

Standards  of  the  Engineers'  and  Surveyors' 

Transit,  sizes  No.   1,  2  and  11. 

In  transits  reading  to  minutes  and  half-minutes,  the  plate-level  in  front  of  the  tele- 
scope is  generally  sufficiently  sensitive  to  insure  good  work.  However,  an  instrument 
of  the  class  as  shown  and  described  under  No.  1  d,  should  always  be  provided  with  a 
striding  level,  to  insure  a  degree  of  accuracy  in  keeping  with  its  greater  capability.  The 
sensitiveness  of  this  striding  level  is  equal  to  that  of  the  long  level  on  the  telescope. 

Thus  it  will  be  seen  that  in  a  transit  of  this  description  the  plate-levels  serve  only 
the  purpose  of  leveling  up  generally,  and  that  in  all  cases  where  the  objects  vary  con- 
siderably in  height,  the  striding  level  only  should  be  depended  on  at  every  sight.  The 
striding  le  el  of  this  instrument  rests  on  two  cylinders  of  equal  diameters,,  at  points 
between  the  standards  on  the  cross-axis  of  the  telescope.  As  shown  in  the  cut,  the 
striding  level  can  be  left  on  the  cross-axis  when  the  telescope  is  revolved  in  altitude. — 
To  verify  the  adjustment  of  the  striding  level  (in  other  words,  to  make  its  axis  parallel 
to  the  cross-axis)  level  up  the  transit  and  bring  the  bubble  to  the  middle  of  its  tube,  re- 
verse the  striding  level  on  the  cylinders  and  see  whether  it  reads  the  same;  if  not,  re- 
move half  the  error  by  the  leveling  screws,  the  other  half  by  the  capstan-headed  screws 
at  the  end  and  repeat  until  corrected.  To  verify  the  side  adjustment  of  the  level,  re- 
volve the  telescope  20  or  30°,  and  note  whether  the  reading  of  the  bubble  remains  the 
same,  if  not,  correct  the  error  by  the  capstan-headed  screws  at  the  side.  To  verify  the 
adjustment  of  the  cross-axis  of  the  telescope  for  right  angles  to  the  vertical  axis  of  the 
transit,  revolve  the  instrument  180°  in  azimuth,  and  assuming  that  both  cylinders,  on 
which  the  striding  level  rests,  are  equal  in  diameter,  a  change  in  the  reading  of  the 
bubble  will  indicate  double  the  amount  of  error.  To  correct  it,  remove  half  the  error 
by  the  leveling  screws,  the  other  half  by  the  Wye  adjustment  of  the  standard. — 


57 

Adjustment  of  the  Improved  Transverse  Striding  Level 

resting-  on  special  collars  for  the  Engineers'  and  Surveyors' 
Transits,  sizes  No.  1,  2  and  11. 

This  striding  level  differs  from  the  one  formerly  made  by  us,  and  referred  to  in  the 
preceding  article,  in  several  respects.  It  permits  of  a  longer  spirit-level  in  the  same 
length  of  outer  tube— so  important  in  this  case  on  account  of  the  short  available  dis- 
tance between  the  collars;  and  is  simpler  in  design,  so  that  after  an  adjustment  has 
been  once  properly  performed,  barring  accidents,  it  hardly  ever  needs  to  be  repeated 
again. 

To  make  a  readjustment:  first  find  out  whether  the  level  needs  a  lateral  adjust- 
ment by  placing  it  on  its  collars  with  instrument  leveled  up,  and  fastening  it  by  the 
milled  headed  nut  to  the  horizontal  axis,  place  the  bubble  in  the  center  of  its  tube  by 
the  leveling  screws,  and  then  elevate  and  depress  the  telescope  10°  to  20°  from  0;  note 
carefully  the  amount  of  displacement  of  bubble,  also  which  one  of  the  two  capstan- 
headed  screws  (one  white  and  one  red,  to  readily  distinguish  one  from  the  other)  must 
be  moved  one-half  the  error;  move  screw  outwardly  if  bubble  must  be  moved  away  from 
this  screw,  and  inwardly  if  bubble  must  be  raised  towards  it  to  make  the  level  tube 
laterally  parallel  to  the  transverse  axis  of  the  telescope.  Then  move  the  other  adjust- 
ing screw  an  equal  amount,  but  in  the  opposite  direction  to  retain  the  same  height  of 
leg,  and  repeat  this  adjustment  until  one-half  the  error  is  corrected.  Before  operating 
any  of  the  adjusting  screws  first  remove  the  level  from  the  collars. 

This  accomplished,  now  make  the  longitudinal  adjustment.  Clamp  the  tele- 
scope in  the  horizontal  position  and  reverse  the  level  on  its  collars;  note  whether  the 
leg  with  the  screws  should  be  raised  or  lowered  to  bring  the  bubble  to  the  center  of  its 
tube,  and  then  turn  each  screw,  alternately,  an  amount  equal  to  one-quarter  the  error 
(inwardly  if  the  leg  is  to  be  raised,  or  outwardly  if  leg  is  to  be  lowered)  in  order  to 
eliminate  one-half  the  error  of  the  level-tube  sought  to  be  corrected.  Then  again  re- 
verse the  level  on  its  collars,  and  repeat  this  adjustment  if  necessary.  If  the  level  has 
been  considerably  out  of  adjustment  it  will  be  well  to  again  verify  the  lateral  adjust- 
ment in  the  manner  prescribed  for  it  above,  and  also  to  repeat  the  longitudinal  adjust- 
ment by  again  following  the  method  just  explained  until  completed. — Remember,  that 
if  the  leg  has  to  be  raised,  both  screws  must  be  moved  inwardly  towards  the  telescope, 
and  that  if  it  has  to  be  lowered,  both  screws  must  be  moved  outwardly  in  equal  amounts. 
This  method  has  been  prescribed  by  us  as  being  the  most  simple  to  follow.  One  some- 
what versed  in  making  adjustments  probably  may  succeed  in  making  it  quicker  (if  the 
level  is  considerably  out)  by  noting  mentally  the  amount  of  displacement  of  bubble  for 
the  longitudinal  and  lateral  adjustments,  and  then  correcting  same  simultaneously,  or 
nearly  so,  with  one  of  the  screws  alone,  by  moving  it  in  the  desired  direction.  To  ad- 
just the  height  of  standards  see  page  54- 

The  Adjustments  of  the  Telescope's  Axis  of  Revolution  in  Transit- 
Theodolites  by  means  of  the  Transverse  Striding-Level  resting 
on  points  of  contact  in  the  Wyes. 

The  striding-level  of  the  finest  class  of  instruments,  such  as  Transit-Theodolites 
used  for  triangulation  wholly,  and  Mining  Transit  used  mainly  for  very  steep  sighting, 
will  rest  directly  upon  the  cylindrical  pivots  of  the  transverse  axis,  at  the  circle  of 
contact  in  the  wyes. 

Whenever  exact  vertical  motion  is  desired,  the  striding-level  in  such  instruments 
should  be  depended  upon  to  the  exclusion  of  the  front  plate-level.  The  latter  is  then 
entirely  subordinate  to  the  striding-level  and  should  be  depended  upon  merely  for  level- 
ing the  instrument  approximately.  The  plate-levels  are  also  useful  in  indicating 
quickly  any  large  disturbances  of  position.  When  the  objects  sighted  at  do  not  differ 
much  in  altitude,  the  front  plate-level  is,  in  these  instruments,  sufficiently  sensitive  to 
give  satisfactory  results  without  using  the  striding-level. 

The  adjustment  of  the  transverse  axis  of  revolution.  The  striding-level 
having  been  carefully  adjusted,  level  up  the  instrument  generally  with  the  plate-levels, 
put  the  striding-level  in  position  and  bring  its  bubble  to  the  center  of  its  graduation 
by  means  of  the  leveling  screws,  then  turn  the  instrument  180°  on  its  vertical  axis  and 
note  whether  the  bubble  of  the  striding-level  remains  in  the  center  of  the  graduation. 
If  it  does,  the  adjustment  is  correct.  If  it  does  not,  correct  one-half  the  error  by  means 
of  the  leveling  screws,  and  the  other  half  by  means  of  the  wye  adjustment  of  the 
standard.  Repeat  the  process  until  the  adjustment  is  correct.  Observe  also,  in  ad- 
justing the  wye  adjustment  of  the  standards,  that  it  will  be  best  performed  and  more 
lasting  when  the  last  turns  of  the  lower  capstan-headed  screw  are  always  applied  in 
an  upward  direction. 


58 


To  adjust  the  line  of  collimatioii  in  Erecting  and 
Inverting  Telescopes. 

NOTE:  —  To  adjust  the  line  of  collimation  in  a  telescope  showing  objects 
erect,  follow  the  simple  rule  that  the  diaphragm  bearing  the  wires  must  be  moved 
in  the  direction  in  which  the  error  is  observed  (as  if  to  increase  the  error)  ; 
in  telescopes  showing  objects  inverted  the  wires  must  be  moved  in  the  direction 
lessening  the  error  observed.  See  diagrams  below. 


Erecting  Telescope. 


FIG.I 


Fio.2 


To  move  the  horizontal  wire  for  collimation  explained  above  it  must  be  under- 
stood that  the  dotted  line  in  the  upper  half  of  the  field  or  view,  Fig.  1,  shows  the  hori- 
zontal wire  where  it  is  actually  situated  on  the  reticule,  but  that  through  the  re- 
versing action  of  the  erecting  eye-piece  the  cross-wire  image  is  reversed  and  therefore 
the  horizontal  wire  is  seen  in  the  lower  half  as  shown  in  the  diagram.  Therefore,  if 
the  horizontal  wire  seen  in  the  lower  half  of  the  diagram  must  be  moved  upwards, 
then  contrary  to  the  appearance,  screw  A  must  be  loosened,  and  B  tightened  an 
equal  amount  in  order  to  bodily  move  the  wire  reticule  towards  the  center  of  the 
stationary  field  of  view  (indicated  by  the  dotted  intersection)  until  one-half  of 
the  error  is  corrected  when  the  wire  will  be  adjusted  and  appear  in  the  center  of  the 
field  of  view, — provided  the  optical  axis  of  the  eye-piece  has  been  previously  cen- 
tered. To  move  the  vertical  wire  for  collimation  explained  on  page  54,  remem- 
ber that  the  dotted  line  at  the  left,  Fig.  2,  shows  the  vertical  wire  where  it  is  actually 
situated  on  the  reticule,  but  that  through  the  reversal  of  the  cross-wire  image  by 
the  use  of  an  erecting  eye-piece  it  is  now  seen  at  the  right  in  the  field  of  view  in  the 
diagram;  therefore,  adjusting  screw  A  must  be  loosened  and  B  tightened  an  equal 
amount  in  order  that  the  reticule  will  bodily  move  towards  B,  when  the  vertical 
wire  seen  at  the  right  will  pass  towards  the  center  of  the  stationary  field  of  view 
(indicated  by  the  dotted  intersection)  until  one-quarter  of  the  error  observed  is 
removed,  when  the  wire  will  be  in  complete  adjustment  at  the  optical  axis. 


Inverting  Telescope. 


RG.3 


B 


FlG.4 


To  move  the  horizontal  wire  for  collimation,  page  54,  the  observed  error  must 
be  corrected  by  moving  the  wire  reticule  one-half  the  amount  hi  the  direction  it  is 
lessened,  when  the  telescope  is  revolved  in  improvised  wyes  as  in  a  wye  level.  Thus, 
Fig.  3,  if  the  wire  must  be  moved  down,  A  must  be  loosened  and  B  tightened  an  equal 
amount. 

To  move  the  vertical  wire  for  collimation  explained  above,  the  observed  error 
must  be  corrected  by  moving  the  wire  recticule  one-quarter  of  the  amount  in  the 
direction  it  is  lessened.  Therefore,  if  the  wire  must  come  to  the  right,  A,  Fig.  4,  must 
be  loosened,  and  B  tightened  an  equal  amount  until  the  object  is  attained. 


39 

THE  WYE  LEVEL. 

The  description  of  the  telescope  of  the  engineer's  transit  applieg  with  the  fol- 
lowing modifications  to  the  telescope  of  this  level. 

It  has  a  clear  aperture  of  13/%  inches  focus,  and  is  17  or  18  inches  long  over  all, 
the  sun-shade  excluded. 

The  bell-metal  collars  which  rest  in  the  wyes  are  about  10J^  inches  apart  and 
1^4  inches  in  diameter. 

On  account  of  the  extreme  length  of  the  telescope  tube,  four  capstan-headed 
screws  are  provided  for  centering  the  eye-piece. 

The  object-glass  focussing  screw  is  in  the  middle  of  the  tube.  The  eye-piece  is 
focussed  by  turning  a  milled  ring  at  the  eye-end.  The  level  attached  to  the  tele- 
scope is  about  8  inches  long,  with  about  5K  inches  exposed,  and  having  a  scale  gradu- 
ated on  glass  for  reading  the  position  of  its  bubble.  The  bubble  is  ground  to  a  true 
curvature  and  barrel  form.  The  sensitiveness  of  spirit  level  is  graded  to  the  class  of 
work  for  which  the  instrument  is  intended.  The  level-tube  is  suspended  from  the 
telescope-tube  in  such  a  manner  that  at  the  object-glass  end  it  can  be  moved  in  azi- 
muth, with  reference  to  the  telescope  axis,  and  at  the  eye-piece  end  it  can  be  moved 
in  altitude  with  reference  to  the  same  axis. 

Its  graduated  scale  is  on  the  level  vial  tube,  and  numbered  from  6  to  0  to  5  at,  each 
end  of  the  bubble. 

The  level-bar  is  about  12  inches  long  over  all,  and  at  its  two  extremities  sup- 
ports the  two  wyes  which  rise  about  3%  inches  from  its  upper  surface.  One  of 
these  wyes  is  adjustable  in  altitude.  The  level-bar  is  attached  to  a  long  conical 
center  of  the  hardest  bell-metal,  which  may  be  clamped  to  the  leveling  plate,  and 
then  a  slow  motion  in  azimuth  may  be  given  to  the  telescope,  by  a  slow  motion 
screw  which  presses  the  clamping  bar  against  a  stiff  spiral  spring.  With  the  sun- 
shade on  the  telescope,  the  weight  is  equaly  distributed  from  the  center,  each  way. 
This  is  necessary,  since  a  sensitive  level,  in  the  nicest  work,  is  affected  by  any 
unequal  strain,  though  it  may  seem  to  be,  practically,  imperceptible. 

The  base,  on  which  the  leveling  screws  rest,  has  as  great  a  diameter  as  porta- 
bility will  permit ;  and  the  leveling  screws  are  cut  with  a  fine  thread.  These  two 
points  add  to  the  ease  with  which  the  instrument  may  be  accurately  leveled. 

A  stop  is  so  arranged  that  the  telescope  may  be  readily  set  with  its  horizontal 
cross-line  level,  when  the  instrument  is  in  adjustment. 

The  instrument  complete  is  not  separable  when  put  into  its  box.  This  condition  is 
necessary  to  protect  one  of  the  essential  adjustments  of  the  level — the  adjustment  of 
the  wyes — from  needless  derangement. 


60 


62 

The  Adjustment  of  the  Wye  Level. 

After  the  engineer  has  set  up  the  instrument  and  adjusted  the  eye-piece  for 
parallax,  as  described  under  the  engineer's  transit,  the  horizontal  cross-wire  had 
better  be  made  to  lie  in  the  plane  of  the  azimuthal  rotation  of  the  instrument. 
This  may  be  accomplished  by  rotating  the  reticule,  after  loosening  the  capstan-headed 
screws,  until  a  point  remains  bi-sected  throughout  the  length  of  the  wire  when  the 
telescope  is  moved  in  azimuth.  In  making  this  adjustment,  the  level  tube  is  to  be 
kept  directly  beneath  the  telescope-tube.  When  made,  the  small  set  screw  attached 
to  one  of  the  wyes  may  be  set  so  that  by  simply  bringing  the  projecting  pin  from  the 
telescope  against  it,  the  cross-wires  will  be  respectively  parallel  and  perpendicular  to 
the  motion  of  the  telescope  in  azimuth. 

The  first  collimating  of  the  telescope  may  be  made  using  an  edge  of  some 
building,  or  any  profile  which  is  vertical.  Make  the  vertical  cross-wire  tangent  to  any 
such  profile,  and  then  turn  the  telescope  half-way  round  in  its  wyes.  If  the  vertical 
cross-wire  is  still  tangent  to  the  edge  selected,  the  vertical  cross-wire  is  collimated. 

To  make  the  adjustment  of  the  horizontal  wire,  select  some  horizontal  line, 
and  cause  the  horizontal  cross-wire  to  be  brought  tangent  to  it.  Again  rotate  the  tele- 
scope half-way  round  in  its  wyes,  and  if  the  horizontal  cross-wire  is  still  tangent  to  the 
edge  selected,  the  horizontal  cross-wire  is  collimated. 

*  Having  adjusted  the  two  wires  separately  in  this  manner,  select  some  well-de- 
fined point  which  the  cross-wires  are  made  to  bi-sect.  Now  rotate  *,he  telescope  half- 
way round  in  its  wyes.  If  the  point  is  still  bi-sected,  the  telescope  is  collimated.  A 
very  excellent  mark  to  use  is  the  intersection  of  the  cross-wires  of  a  transit  instrument 
using  same  as  a  collimator. 

To  center  the  eye-piece  by  the  four  capstan-headed  screws  nearest  the  eye  end : 
This  is  done  by  moving  the  opposite  screws  in  the  same  direction  until  a  distant  object 
under  observation  is  without  the  appearance  of  a  rise  or  fall  throughout  an  entire  rota- 
tion of  the  telescope  in  its  wyes.  The  telescope  is  now  adjusted. 

To  adjust  the  spirit  level  to  the  telescope,  bring  the  level  bar  over  two  of  the 
leveling  screws,  focus  the  telescope  upon  some  object  about  300  feet  distant,  and  put 
on  the  sun-shade.  These  precautions  are  necessary  to  a  nice  adjustment  of  the  level 
tube.  Throw  open  the  two  arms  which  hold  the  telescope  down  in  its  wyes,  and  care- 
fully level  the  instrument  over  the  two  level  screws  parallel  to  the  telescope.  Lift  the 
telescope  out  of  its  wyes,  turn  it  end  for  end  and  carefully  replace  it.  If  the  level  tube 
is  adjusted,  the  level  will  indicate  the  same  reading  as  before.  If  it  does  not,  correct 
half  the  deviation  by  the  two  leveling  screws  and  the  remainder  by  moving  the  level 
tube  vertically  by  means  of  the  two  adjusting  nuts  which  secure  the  level  tube  to  the 
telescope  tube  at  its  eye-piece  end.  Loosen  the  upper  nut  with  an  adjusting  pin,  and 
then  raise  or  lower  the  lower  nut  as  the  case  requires,  and  finally  clamp  that  end  of 
the  level  tube  by  bringing  home  the  upper  nut.  This  adjustment  may  require  several 
repetitions  before  it  is  perfect. 

To  make  the  lateral  adjustment  of  the  spirit  level :  The  level  is  now  to  be  ad- 
justed so  that  its  axis  may  be  parallel  to  the  axis  of  the  telescope.  Kotate  the  tele- 
scope about  20°  in  its  wyes,  and  note  whether  the  level  bubble  has  the  same  reading 
as  when  the  bubble  was  wider  the  telescope.  If  it  has,  this  adjustment  is  made.  If  it 
has  not  the  same  reading,  move  the  end  of  the  level  tube  nearest  the  object-glass  in  a 
horizontal  direction,  when  the  telescope  is  in  its  proper  position,  by  means  of  the  two 
small  horizontal  caps  tan- headed  screws  which  secure  that  end  of  the  level  to  the  tele- 
scope tube.  If  the  level  bubble  goes  to  the  object-glass  end  when  that  end  is  to  the 
engineer's  right  hand,  upon  rotating  the  telescope  level  toward  him,  then  these  screws 
are  to  be  turned  in  the  direction  of  a  left-handed  screw,  as  the  engineer  sees  them,  and 
vice  versa.  This  accomplished  the  vertical  adjustment  of  the  spirit  level  for  parallelism 
with  the  line  of  collimation  of  the  horizontal  wire  must  now  again  be  verified.  Having 
completed  this  adjustment,  the  level  bar  itself  must  now  be  made  parallel  to  the  axis 
of  the  level. 

To  make  the  adjustment  of  the  level  bar:  Level  the  instrument  carefully 
over  two  of  its  leveling  screws,  the  other  two  being  set  as  nearly  level  as  may  be;  turn 
the  instrument  180°  in  azimuth,  and  if  the  level  indicates  the  same  inclination,  the 
level  bar  is  adjusted,  If  the  level  bubble  indicates  a  change  of  inclination  of  the  tele- 
scope in  turning  180°,  correct  half  the  amount  of  the  change  by  the  two  level  screws, 
and  the  remainder  by  the  two  capstan-headed  nuts  at  the  end  of  the  level  bar.  Turn  both 
nuts  in  the  same  direction,  an  equal  part  of  a  revolution,  starting  that  nut  first  which 
is  in  the  direction  of  the  desired  movement  of  the  level  bar.  Many  engineers  consider 
this  adjustment  of  little  importance,  prefering  to  bring  the  level  bubble  in  the  middle 
of  its  tube  at  each  sight  by  means  of  the  leveling  screws  alone,  rather  than  to  give  any 
great  consideration  to  this  adjustment,  should  it  require  to  be  made. 

*  See  page  58. 


63 

THE  DUMPY  LEVEL. 

(For  description  and  cuts  see  pages  123  to  129.) 

Adjusting1. 

Two-Peg  Method. 

A  theoretically  perfect  dumpy  level  has  the  same  points  established  that  are 
mentioned  under  the  head  of  wye  level;  but  since  its  construction  differs  from  the 
wye  level,  the  methods  of  adjustment  are  not  so  convenient,  resembling  closely  the 
adjustment  of  the  transit  telescope  and  its  attached  level.  After  attaching  the  sun- 
shade remove  parallax  by  pointing  the  telescope  to  the  sky,  and  turn  the  eye-piece  un- 
til the  cross  hairs  are  sharp  and  distinct.  Since  the  eye  itself  may  have  slightly 
accommodated  itself  to  the  eye-piece,  test  the  adjustment  by  looking  with  the  unaided 
eye  at  some  distant  point,  and  while  still  looking,  bring  the  eye-piece  of  the  telescope 
before  the  eye.  If  the  cross  hairs  are  sharp  at  the  first  glance,  the  adjustment  is  made. 
Now  focus  in  the  usual  manner  upon  any  object,  bringing  the  cross  hairs  and  image  to 
a  sharp  focus  by  the  rack-work  alone.  A  point  should  remain  bi-sected  when  the  eye 
is  moved  from  one  side  of  the  eye-piece  to  the  other. 

To  place  the  horizontal  cross  wire  at  right  angles  to  the  vertical  center  bi-sect 
some  well-defined  object  such  as  a  chimney  top,  top  of  roof,  fence-rail  or  window-sill 
(the  best  views  are  against  the  sky  for  a  background)  and  move  the  telescope  on  its 
vertical  center.  If  the  horizontal  wire  bi-sects  the  point  throughout  its  entire  field  of 
view  it  is  adjusted. 

If  it  does  not  slightly  loosen  the  four  capstan-headed  adjusting  screws  (in  the 
inverting  telescope  those  nearest  the  eye-piece  or  the  further  set  from  the  eye  when 
the  telescope  shows  objects  erect)  and  turn  the  wire  diaphragm  until  the  selected 
point  remains  bi-sected  when  the  telescope  is  moved  in  azimuth  throughout  the  entire 
field  of  view. 

To  adjust  the  level,  bring  the  level  over  two  of  its  foot  screws,  and  bring  the 
bubble  to  the  middle  of  its  tube  by  means  of  the  foot  screws  alone.  Revolve  the 
instrument  180°  in  azimuth,  and  if  the  bubble  remains  in  the  middle  it  is  adjusted, 
if  it  does  not,  then  correct  half  its  deviation  by  the  capstan-headed  adjusting  screw 
of  the  spirit  level,  and  the  remaining  half  by  the  two  foot  screws.  Repeat  the  opera- 
tion over  the  other  two  screws,  until  the  instrument  may  be  revolved  in  any  position, 
and  the  level  bubble  will  remain  in  the  middle  of  its  tube. 

To  adjust  the  horizontal  wire  so  that  the  line  of  sight  will  be  parallel  to 
the  spirit  level,  one  method  is  to  use  a  sheet  of  water,  or  where  that  is  not  available, 
two  stakes  which  are  driven  with  their  surfaces  in  the  same  level  plane. 

To  make  the  adjustment  with  the  stakes,  set  up  the  level  half  way  between  two 
points  lyin?  very  nearly  in  a  horizontal  line,  and  say  300  feet  apart.  Drive  a  stake 
at  one  of  these  points,  place  the  rod  on  it  and  take  a  reading,  first  bringing  the  bubble 
to  the  middle  of  its  tube.  Point  the  telescope  in  the  opposite  direction,  again  bring 
the  bubble  to  the  middle  of  its  tube,  and  drive  a  second  stake  at  the  second  point 
selected  until  the  rod  held  upon  the  second  stake  gives  the  same  reading  as  when 
held  upon  the  first  stake.  The  tops  of  these  two  stakes  now  lie  in  the  same  Level  line. 

Take  up  the  level  and  set  it  outside  in  line  as  near  as  it  can  be  f  ocussed  on  the  first 
stake  and  level  up.  Now  read  the  rod  upon  the  first  stake,  and  then  upon  the  second.  If 
the  two  readings  agree,  and  the  bubble  is  in  the  middle  of  its  tube,  the  collimation  is  cor- 
rect. If  the  two  readings  do  not  agree,  change  the  horizontal  wire*  to  read  the  same 
on  the  distant  rod  by  means  of  the  capstan-headed  screws  near  the  eye-piece  in  the 
inverting  telescope  and  furthest  from  the  eye-piece  in  the  erecting  telescope.  Refocus 
on  the  nearest  rod,  take  a  reading,  then  focus  on  the  distant  rod  and  again  by  means  of 
the  capstan-headed  adjusting  screws,  make  the  horizontal  wire  read  the  same.  Repeat 
this  operation  until  both  rods  read  the  same,  with  the  bubble  in  the  middle  of  its  tube. 

The  telescope  and  uprights  are  in  a  single  casting,  which  is  finished  and  fitted  to 
the  level  bar,  so  that  the  line  of  collimation  may  be  permanently  parallel  to  it. 

The  dumpy  level  will  then  be  in  adjustment,  since  the  adjustment  of  its  vertical 
cross  line  is  of  no  importance. 

Adjustment  of  the  Dumpy  Level1— and  attached  level  of 
Transit  Telescope. 

Two-Peg  Method. 

The  following  method  is  simple,  direct,  and  geometrically  accurate,  requiring  no 
approximate  measurements  from  a  peg  to  the  center  of  lens,  no  trial  setting  of  the  tele- 
scope, no  trials  to  drive  a  peg  just  enough  and  not  too  far,  and  no  auxiliaries  except 
level-rod  and  tape  or  chain. 

Contributed  by  Prof.  R.  Fletcher,  Thayer  School  Dartmouth  College. 
*  See  page  58. 


On  slightly  rising  ground  locate  four  points  a,  6,  c  and  d,  on  the  same  line,  nearly, 
making  be  =  ca,  and  ad  any  convenient  distance,  preferably  not  much  less  than  ca,  and 
in  some  simple  ratio  with  it,  for  ease  of  calculation  afterwards.  Set  the  instrument  at 
c ;  take  readings  A'  and  B'  on  a  and  b  respectively,  carefully  leveling  before  each  sight. 
Then,  unless  the  instrument  is  otherwise  much  out  of  adjustment,  (B'— A')  is  the  true 
difference  of  level  of  a  and  b. 

Next  set  up  at  d,  level  carefully,  and  take  readings  A"  and  B'"  on  a  and  b  respec- 
tively. [In  strictness  the  centre  of  the  instrument  should  not  be  set  over  d,  but  beyond, 
by  an  additional  distance  =  principal  focal  length  of  the  object-lens  -j-  the  distance  from 
that  lens  to  the  centre  of  the  tripod.  (See  the  Manual,  page  87,  Fig.  2.)  ]  Then  (B"  — 
A")  —  (B'  —  A')  =  B'"=  error  of  collimation  in  the  distance  ba,  that  is  the  error  due  to 
the  vertical  angle  between  the  line  of  sight  and  axis  of  spirit-level.  Now,  by  similar 
triangles,  we  have  B/,, .  6a  =  BIV  :  ^  ...  B"  =  B///  x  bd , 

ba 

which  is  the  error  in  the  distance  bd,  and  is  to  be  applied  to  the  reading  ~Bff.      Set  the 
rod  to  read  (B" — B1V).    Then : 

For  Adjustment  of  a  Dumpy  Level. 

Having  first  adjusted  the  spirit-level  so  that  it  remains  true  in  all  positions  about 
the  vertical  axis,  point  the  telescope  on  the  rod,  properly  held  at  6,  with  target  set  to 
read  (B" — Blv).  By  means  of  the  capstan-headed  screws,  raise  or  lower  the  horizontal 
line  until  it  bisects  the  target.  To  test  the  adjustment,  set  the  rod  over  a,  with  index 
reading  (B"—  BIV)  —  (B'  —  A'),  and  see  if  the  target  is  still  bisected. 

Adjustment  of  Attached  Level  of  Transit  Telescope. 

The  rod  being  held  plumb  at  b,  with  target  set  to  read  (B" —  Biv),  move  the  tele- 
scope by  vertical  tangent-screw  until  the  line  of  sight  bisects  the  target ;  clamp  securely. 
Then  bring  the  bubble  to  the  middle  of  the  tube  by  means  of  the  level- adjusting  nuts 
alone.  Test  as  in  the  other  case. 

KEMARKS.  —  The  diagram  shows  a  special  case,  viz.,  when  (B"  —  A")  >  (B'  — A'), 
or  the  angle  subtended  by  Bvi  is  one  of  elevation.  If  (B"  — A")  =  (B'  —  A)  the  line  of 
sight  is  already  level  and  no  adjustment  is  needed.  If  (B"  —  A")  <  (B'  -  A?),  B*  sub- 
tends an  angle  of  depression,  and  is  to  be  added  to  B".  In  the  latter  case,  if  the  slope 
of  the  ground  is  slight,  the  difference  (B"  —  A")  may  be  either  zero  or  a  very  small 
quantity,  positive  or  negative ;  but  in  all  cases  it  is  added  algebraically  to  (B'—  A')  to 
obtain  B"7. 

As  in  all  other  methods  of  adjustment,  we  assume  that  the  maker  has  done  his  part 
so  well  that  the  line  of  collimation  will  not  be  disturbed  in  any  movement  of  the  ob- 
jective for  focusing.  Let  us  suppose  that  the  line  of  collimation  is  made  truly  hori- 
zontal, and  that  in  its  prolongation  we  have  set  the  centres  of  two  targets,  one  over  a 
and  one  over  6,  the  instrument  being  at  d.  If  now  we  focus  upon  the  farther  target,  the 
image  will  be  bisected  by  the  horizontal  spider-line.  Then  change  the  focus  so  as  to 
view  the  nearer  target.  If  the  centre  of  the  objective  has  not  moved  truly  in  the  line  of 
collimation,  the  new  image  will  not  be  bisected  at  the  focus,  and  the  nearer  target  will 
appear  to  be  out  of  level,  when  in  fact  it  is  not.  Hence,  since  this  adjustment  requires 
change  of  focus,  it  cannot  be  made  if  the  above  defect,  in  the  movement  of  the  objective, 
exists.  If,  however,  the  distance  ad  be  not  too  small  and  the  defect  alluded  to  be  only 
slight,  the  error  in  changing  focus  for  b  and  a  may  be  hardly  appreciable.  The  adjust- 
ment once  made  approximately,  we  n^ed  not  remark  that,  in  the  field  work,  any  further 
error  of  objective  is  avoided  when  taking  equidistant  sights. 


65 


The  Surveyor's  Solar  Attachment. 

Written  for  this  catalogue  by'H.  C.  PEARSONS,  C.  E.,  Ferrysburg,  Mich. 

The  "  Solar  Attachment,"  of  which  the  following  is  a  description,  is  a  modification 
of  Peat  son's  Solar  Transit. 

With  the  view  of  reducing  the  weighf  and  cost  of  this  attachment,  the  declination 
arc  is  dispensed  with,  using,  in  its  stead,  the  latitude  arc  for  setting  off  the  dec- 
lination. 

And  to  attain  a  greater  degree  of  precision,  a  small  telescope  with  cross-hairs,  and 
a  diagonal  eye-piece  have  been  introduced  in  place  of  the  lens-bar  and  focal-plate. 

This  attachment  is  an  appliance  to  the  surveyor's  transit  for  the  purpose  of 
finding  the  astronomical  meridian.  Combined  with  that  instrument,  it  becomes 
purely  astronomical  in  its  character  —  indeed,  a  portable  Equatorial,  and  an  Alt.- 
Azimuth  instrument  combined,  —  hence  a  few  astronomical  definitions  seem  tc 
oe  requisite. 


In  the  accompanying  cut,  the  instrument  is  represented  in  position  for  an  ob- 
servation ;  and  in  north  latitude  (as  in  these  instructions  we  will  suppose  the  observer 
to  be)  the  view  is  as  from  the  west. 

(1.)  The  line  through  the  vertical  axis  of  the  transit  represents  the  pole  of 
horizon,  and  is  called  the  Vertical. 

The  line  perpendicular  to  this  represents  the  Horizon. 

(2.)  The  transit  telescope,  having  its  optical  axis  in  the  meridian,  and  having 
its  south  end  (whether  object-end  or  eye-end)  elevated  so  that  the  vertical-arc  reads 
the  co-latitude,  will  have  its  optical  axis  in  the  plane  of  the  equator  also;  viz.  the 
optical  axis  of  the  telescope  will  then  represent  the  intersection  of  the  plane  of  the 
meridian,  with  that  of  the  equator.  This  line  is  called  the  Equator. 

(3.)  The  line  perpendicular  to  the  equator,  —  that  around  which  the  solar 
telescope  revolves,  in  following  the  sun  in  his  diurnal  course,  is  the  pole  of  the 
equator.  —  It  is  parallel  with  the  earth's  axis,  and  is  called  the  Polar  Axis. 

(4.)  The  arc  distance  from  the  equator  to  the  vertical  is  the  Latitude  of  the  ob- 
server, —  whence  the  distance  from  the  vertical  to  the  polar  axis,  is  the  Co-Latitude. 

It  will  be  observed  that  these  arcs  occur  alternately  around  the  entire  circle;  so 
that  the  student  should  make  himself  familiar  with  their  relative  position  with  regard 
to  the  horizon,  and  the  vertical,  in  order  to  avoid  mistakes,  when  setting  the  polar 
axis  of  the  instrument  up  to  the  pole  of  the  equator. 


(5.)  Astronomical  Triangle.  The  height  of  the  sun  is  measured  in  a  plane  passing 
through  the  "  Vertical  "  and  the  sun,  and  is  called  his  Altitude,  whence  his  distance 
from  the  "  Vertical  "  is  his  Co-  Altitude. 

In  the  same  manner,  the  distance  from  the  sun  to  the  "Pole,"  is  his  co-dec- 
lination; and  the  distance  from  the  ."  Vertical  "  to  the  pole,  is  the  observer's  Co- 
Latitude.  These  three  compliments  form  what  is  called  the  Astronomical  Triangle. 

Thus  we  have  the  three  sides  of  a  spherical  triangle,  from  which  to  find  the 
several  angles. 

(6.)  The  angle  at  the  Pole,  contained  between  the  meridian  of  the  observer  and 
that  passing  through  the  sun,  is  called  the  Hour  Angle,  as  it  gives  the  distance  from 
the  sun  to  the  observer's  meridian,  in  time  or  arc,  and  is  usually  represented  by  the 
letter  H. 

(7.)  The  angle  at  the  "Vertical,"  or  at  the  observer's  zenith,  contained  between 
the  meridian  and  a  vertical  plane  passing  through  the  sun,  is  called  the  Azimuth 
Angle,  and  is  usually  represented  bv  the  letter  Z. 

This  angle  is  the  one  particularly  important  to  surveyors,  as  from  it  the  place  of 
the  meridian  is  readily  determined. 

Navigator's  look  for  this  angle  every  day,  when  an  observation  can  be  had,  and 
solve  the  triangle  for  Z,  by  one  or  both  of  the  following  equations. 

cosS    cos(S  —  p)\| 

......      (a.) 


.  (b.) 

'  v    > 

in  which 

L  =  Latitude.  Z  =  the  required  Azimuth 

d  =  Declination.  p  =  Polar  Distance  =  90°—  d. 

h  =  Height  of  the  sun's  center,  corrected  for  refraction  and  parallax. 


NOTB.  —  The  correction  for  parallax,  which  is  usually  about  6".  and  never  exceeds  9",  may  be  neglected 
•xcept  in  work  of  great  precision. 

To  solve  these  equations  numerically  requires  much  computation,  but  the  Solar 
Transit  solves  them  for  Z,  mechanically,  with  no  more  computation  than  that  required 
to  deduce  the  declination  for  the  longitude  and  local  time  of  the  observer,  from  that 
given  in  the  Nautical  Almanac  for  the  day. 

From  the  above  definitions,  it  is  readily  seen  that  the  following  conditions,  or 
relation  between  the  parts  of  the  instrument,  must  be  established. 

(A.)  The  polar  axis  must  be  Vertical,  when  the  vertical  arc  (latitude  arc)  reads 
zero,  and,  consequently,  perpendicular  to  the  cross  axis  of  the  transit  telescope. 

(B.)  The  horizontal  cross-wire  of  the  solar  telescope  must  be  parallel  with  the 
plane  of  its  rotation  around  the  polar  axis;  i.e.  it  must  be  parallel  with  the  plane 
of  the  equator. 

(C.~)  The  plane  passing  through  the  vertical  wire  and  the  optical  axis  of  the 
solar  telescope  must  be  at  right  angles  to  the  cross  axis  of  the  solar  telescope. 

(D.)  The  bubble  of  the  level-tube  on  the  solar  telescope  must  be  in  the  middle 
of  its  tube,  when  the  optical  axis  of  that  telescope  is  in  the  plane  of  the  horizon. 

These  conditions  are  obtained  by  the  following 

Adjustments. 

Having  attached  tL?  '•  Solar"  to  the  cross  axis  of  the  telescope,  as  directed  under 
the  head  of  "Remarks,"  and  having  leveled  up  the  transit  (supposed  to  be  in  perfect 
adjustment)  carefully,  set  the  vertical  or  latitude  arc  to  zero,  observing  that,  upon 
rotating  the  whole  instrument  180°  in  azimuth,  the  bubble  of  the  level  of  the  transit 
telescope  is  in  the  middle  of  the  tube.  Bring  the  level  bubble  of  the  solar  telescope  to 
the  middle  of  the  tube  by  means  of  the  clamp  and  opposing  tangent  screws  of  the 
solar  telescope  ;  then  revolve  the  solar  telescope  on  its  polar  axis  180°  to  see  if  its 
bubble  remains  in  the  center  of  its  tube  :  if  not,  remove  half  its  error  by  means  of  the 
opposing  tangent  screws,  the  other  half  by  the  milled  capstan-headed  screws  below 
the  base-plate,  until  it  remains  in  the  center  of  the  tube.  Repeat  if  necessary. 

Turn  the  solar  telescope  90°  on  its  polar  axis,  and  by  the  milled  capstan-headed 
screw  level  the  base-plate  and  bring  the  bubble  to  the  center  of  the  tube.  Repeat 
the  operation  until  the  bubble  of  the  solar  telescope  remains  in  the  center  of  the  tube 
upon  revolving  the  solar  telescope  around  its  polar  axis.  (This  condition  must  be 
attained  before  the  polar  axis  can  be  set  to  the  co-latitude  of  the  observer  ;  and  being 
.attained  it  needs  no  further  attention  than  being  examined  at  times  for  verification). 


67 

The  adjustment  of  the  polar  axis  to  be  truly  at  right  angles  to  the  line  of  sight  of 
the  main  telescope  is  made  by  two  milled  capstan-headed  screws  and  two  opposing 
springs  at  right  angles  to  each  other  below  the  base  or  leveling  plate  of  the  solar 
attachment.  As  will  be  seen  in  making  this  adjustment  it  is  not  necessary  to  place 
the  solar  telescope  parallel  or  at  right  angles  to  the  main  telescope,  but  simply  in  the 
same  vertical  plane  of  each  set  of  leveling  screws  and  springs  at  the  time.  This 
adjustment  is  made  by  the  manufacturer  and  thereafter  needs  only  to  be  examined 
at  times. 

If  the  adjustments  are  properly  made  the  bubble  of  the  level  of  the  transit  telescope 
and  those  of  the  plate  levels  on  the  transit  will  all  be  in  the  center  of  their  tubes,  and  the 
vertical  arc  will  read  zero. 

Bisect  some  convenient  object,  and  turn  the  solar  telescope  sufficiently  to  the  right 
or  left,  around  the  polar  axis,  to  make  the  image  of  the  object  traverse  the  field  from 
one  side  of  the  tube  to  the  other.  The  image  should  remain  bisected  by  the  wire, 
If  not,  loosen  the  four  capstan-headed  screws  of  the  diaphragm  till  the  above  condition 
is  attained,  and  fasten  the  screws  securely, 

The  solar  telescope  showing  usually  objects  inverted,  requires  the  cross-wire  dia- 
phragm to  be  moved  as  described  on  page  58  of  Manual. 

Bisect  any  very  distant  object  in  the  horizontal  plane  by  the  main  telescope,  and 
clamp.  Then,  by  means  of  the  clamp  and  opposing  tangent  screws  on  the  solar  teles- 
cope, bring  its  horizontal  cross-wire  to  bisect  the  same  object ;  then,  by  means  of  the 
capstan-headed  screw  of  the  solar  telescope  level  bring  the  bubble  to  the  middle  of 
its  tube.  This  being  done,  the  optical  axes  of  the  two  telescopes  will  lie  in  parallel 
planes  for  distant  objects  and  the  instrument  is  ready  for  use. 

All  these  adjustments  are  made  by  the  manufacturer,  and  need  to  be  verified  only 
occasionally. 

Before  the  solar  attachment  is  available  for  finding  meridian,  the  observer  must 
know  his  Latitude,  and  the  sun's  Declination  for  the  day  and  hour  of  observation, 
corrected  for  refraction,  whence  the 


Reduction  of  Declination  and  Refraction, 

The  sun's  Declination  is  given  for  noon  of  every  day  in  the  year,  in  the  Washing- 
ton and  Greenwich  Ephemeris  of  the  sun,  for  those  meridians.  The  maps  and  charts 
In  use  will  give  the  difference  of  Longitude  to  all  the  precision  required,  and  tables  in 
this  manual  give  the  required  Refraction. 

An  example  will  best  illustrate  : 

Required  a  declination  table  for  the  different  hours  of  the  day  for  April  25,  1885. 
Lat.  44°  N.,  and  Longitude  97°  W.  At  15°  to  the  hour,  97°  of  longitude  is  about 
6 1  hours  of  time,  and  as  this  longitude  is  W.,  12  o'clock,  or  noon,  at  Greenwich  will 
correspond  to  5J^  A.  M.  at  the  place  of  the  observer. 

The  declination,  as  given  for  that  day,  in  the  Greenwich  Ephemeris,  is  13°  20' 
04"  N  ,  and  is  shown  to  be  gaining  at  the  rate  of  49"  per  hour  (see  column  headed 
Difference  for  one  Hour,  with  the  signs  -f-  for  sun  going  North,  and  —  for  SUB 
going  South). 

If  now,  to  the  decimation  for  5|  A.M.,  we  add  the  hourly  rate  of  change  succes- 
sively, we  shall  have  the  declination  for  the  several  hours  of  the  day,  observing  that 
the  first  increment  is  for  only  half  an  hour,  thus  :  — 

Form  of  Daily  Declination  Table. 

APRIL  25,  1885. 

Hourly  difference  Dec.  -f-  49"  j  Hourly  difference  +  49" 

Dec.  5£  A.  M.  N.    .     .     .     13°  20'  04"  +  :    1  p.  M.  N.  . 

6  ...  13  20  28  -f   2 

7  ...  13  21  17  4-   3 

4 
5 
6 
7 


10 
11 
M. 


13  21  17  4- 

13  22  06  + 

13  22  55  + 

13  23  44  4- 

13  24  33  + 

13  25  22  4- 


Dec.  =  13°  26'  11"  + 

"  =13  27  00  -j- 

"  =13  27  49  + 

"  =13  28  38  + 

"  =13  29  27  + 

"  =13  30  16  + 

"  =13  31  05  + 


The  above  table  must  be  corrected  for  the  effects  of  refraction,  before  it  is  set  off 
on  the  vertical  arc  of  the  transit.    Kefraction  increases  the  apparent  altitude  of  an 

object,  and  thereby  affects  the  declination  of  the  object  —  ^hn'shing  [ the  declina- 
tion  when  of  the  Afferent  1  name  with  the  latitude. 


68 

From  the  -(-  sign  of  the  "  difference"  of  declination,  we  see  that  the  decimation  is 
of  the  same  name  as  the  latitude,  whence  the  correction  is  an  increment,  and  accordingly 
the  -f-  sign  as  suffixed.  This  sign  belongs  to  the  refraction. 

When  the  object  is  in  the  meridian,  refraction  a.ffects  declination  by  its  full 
amount;  but,  if  both  the  observer  and  the  object  were  in  the  plane  of  the  equator, 
refraction  would  have  no  effect  on  the  object  with  regard  to  refraction ;  whence,  be- 
tween these  limits,  only  a  part  of  refraction  is  effective  in  changing  the  declination. 

Just  what  portion  is  effective,  is  shown  by  table  II.  of  this  paper. 

Thus,  in  the  given  Lat.  44°,  and  for,  say  4  hours  from  noon,  the  percentage  of  re- 
fraction to  be  applied  is  .74  of  that  corresponding  to  the  altitude  of  the  object  at  the 
time  of  observation.  The  sign  ^  to  be  used  must  be  determined,  as  above,  by  con- 
sidering whether  the  sun  is  going  north  or  south  at  the  time. 

This  part  of  the  reduction  of  declination  cannot,  of  course,  be  made  till  the  alti- 
tude is  found  at  the  time  of  observation. 

To  Find  the  Latitude. 

Having  prepared  the  declination  for  the  day,  as  above,  level  up  the  transit  care- 
fully. Level  the  main  telescope,  observing  that  the  vertical  arc  reads  zero,  arid  set 
the  polar  axis  to  a  vertical  position  by  means  of  the  solar  telescope  level. 

These  points  being  attained,  set  the  main  telescope,  pointing  south.    Then  for  a 

south  [declination>  elevate  |the  south  end  of  the  te1680^6.  tin  the  vertical  arc  in- 
dicates the  declination  thus  found. 

Then,  having  turned  the  solar  telescope  into  a  vertical  plane  parallel  with  that 
containing  the  optical  axis  of  the  main  telescope,  level  it  carefully  and  clamp  it. 

A  few  minutes  before  the  time  of  the  sun's  culmination,  bring  the  telescope  into 
the  vertical  plane  passing  through  the  observer  and  the  sun,  and  "find  the  sun1'  with 
the  solar  telescope.  This  is  readily  done  by  varying  the  altitude  when  the  sun's 
image  will  appear  on  the  diagonal  eye-piece. 

Having  "found  the  sun,"  bisect  his  image  with  the  vertical  wire,  by  varying  the 
azimuth  with  the  tangent  screw  of  the  transit  plate,  or  with  that  of  the  outer  center; 
and,  simultaneously,  follow  him  in  altitude  —  the  horizontal  wire  bisecting  the  image 
—  till  it  ceases  to  rise,  then  clamp  and  read  the  vertical  arc.  This  reading  should 
be  the  sum  of  the  co-latitude  and  refraction,  the  refraction  being  that  due  to  the  meridian 
altitude  of  the  sun,  which  is  the  algebraic  sum  of  declination  and  co-latitude.  From 
this  reading  the  latitude  is  readily  deduced.  With  the  latitude  and  declination 
known,  we  are  prepared 

To  Find  the  Meridian. 

(a.)  As  for  finding  latitude,  level  up  the  instrument  carefully,  the  vernier  of  plate 
«lamped,  reading  zero. 

(b.)  Point  the  telescope  to  the  sun  to  find  his  altitude  for  the  refraction.  This 
can  be  found  with  sufficient  accuracy  by  turning  the  telescope,  till  the  shadow  of  a 
pencil  held  across  the  end,  or  till  the  shadow  of  the  screws  on  the  side,  are  parallel 
with  the  tube. 

(c.)  The  refraction  corresponding  to  this  altitude  must  be  multiplied  by  the  cor- 
responding coefficient,  for  the  time  from  noon  and  the  latitude,  and  applied  to  the 
declination,  as  per  instructions  above,  for  the  corrected  declination. 

(d.)  Point  the  telescope  to  the  south,  ^evithi'g  ) tne  south  end  for  south  |  decli' 
nation,  till  the  vertical  arc  reads  the  corrected  declination,  and  clamp  the  vertical 
arc. 

(e.)  The  main  telescope  being  dipped  to  the  corrected  declination,  level  the  solar 
telescope  by  means  of  its  level,  being  careful  to  do  so  when  it  is  in  a  vertical  plane 
parallel  with  that  containing  the  optical  axis  of  the  main  telescope,  for  only  when  it 
is  in  this  plane  can  the  declination  be  properly  set  off. 

(f.)  Elevate  the  south  end  of  the  main  telescope  to  the  co-latitude,  by  means  of 
the  vertical  arc,  and  turn  the  telescope  approximately  into  the  meridian,  by  means 
of  tb«  magnetic  needle. 

(g.)  "  Find  the  sun  "  with  the  solar  telescope.  This  is  done  by  turning  the  whole  in- 
strument in  azimuth,  on  its  outer  center,  simultaneously  with  a  motion  of  the  solar  teles- 
cope in  right  ascension,  till  the  sun's  image  is  seen  in  the  eye-end  of  solar  telescope. 
Bisect  the  image,  as  nearly  as  may  be,  by  the  two  motions  above  named  —  clamp 
and  complete  the  bisection,  by  both  wires,  or  by  the  wires  forming  a  square,  by  means 
of  the  transit's  lower  tangent  screw,  and  by  that  of  the  solar  telescope.  If  the  image 
of  the  sun  should  be  so  large  that  it  cannot  all  be  seen  from  one  position  of  the  eye. 


look  around  it  by  moving  the  eye  around  it  in  such  a  manner  as  to  see  the  entire  cir- 
cumference, and  bring  the  cross-wires  on  the  four  sides  of  the  image  normal  to  their 
respective  sides,  by  means  of  the  motion  hi  azimuth  and  the  motion  of  the  solar 
telescope,  as  above  described.  This  being  attained,  the  optical  axis  of  the  main  teles- 
cope should  be  in  the  astronomical  meridian.  Refer  to  an  azimuth  mark,  and  repeat 
the  operation.  The  above  is  called  a  direct  observation. 

(h.)  To  make  a  reverse  observation.  Having  made  the  direct  observation,  turn  the 
whole  instrument  180  °  in  azimuth,  and  set  the  co-latitude  off  on  the  opposite  side 
of  the  vertical  arc.  Also  turn  the  solar  telescope  180  °,  and  proceed  as  before.  The 
object  of  repetition  is  to  eliminate  personal  non-precision  and  nossible  errors  in 
manipulation,  while  the  object  of  reversing  is  to  eliminate  any  possible  remaining 
errors  of  adjustment  of  the  instrument.  The  prudent  surveyor  will  not  trust  his  work 
without  such  verification,  and  he  will  take  the  mean  of  both  observations. 

Remarks. 

(1.)  To  unscrew  the  solar  attachment  from  the  packing-piece  in  the  box,  first 
release  the  clamp  and  tangent  screw,  and  then  turn  carefully  the  milled-edged  disk  or 
base  plate  a  few  turns  to  the  left.  To  screw  the  solar  attachment  to  the  instrument, 
turn  this  milled-edged  disk  from  left  to  right  around  the  screw  on  top  of  the  main 
telescope  without  revolving  the  solar  attachment.  To  insure  a  perfect  contact  of 
screw-shoulder  against  the  flange,  on  which  depends  the  permanency  of  the  adjust- 
ment of  the  polar  axis  to  the  main  telescope,  it  is  necessary  that  these  parts  be  free 
from  dust,  grit,  or  dirt  of  any  kind. 

(2.)  The  auxiliary  or  latitude  level,  if  one  is  ordered,  attaches  in  the  same  manner 
to  the  end  of  the  cross  axis  on  the  side  of  the  vertical  circle. 

(3.)  The  latitude  level  is  used  to  facilitate  during  repeated  observations  the  reset- 
ting of  the  polar  axis  to  the  co-latitude,  assuming  that  the  polar  axis  has  been  pre- 
viously set  to  be  at  right  angles  to  the  main  telescope  by  its  milled  capstan-headed 
screws  and  the  solar  level,  the  polar  axis  being  placed  in  its  position  for  an  observation 
with  more  facility  and  precision  with  this  level  than  by  reading  the  vertical  arc. 

(6.)  The  latitude  having  been  found  for  the  initial  point  of  a  survey,  it  may  be 
found  for  other  points  within  moderate  limits  by  allowing  92  chains  of  northing  or 
southing  for  1'  of  latitude. 

(7.)  The  object  of  bringing  the  main  telescope  into  the  meridian  by  means  of 
motion  on  the  outer  spindle  is  to  have  the  zero  line  of  the  horizontal  plate  hi  the 
meridian,  so  that  the  azimuth  or  bearing  of  lines  can  be  referred  to  that  line. 

(8.)  If  for  any  cause  one  is  obliged  to  work  with  an  uncertain  latitude,  it  is  better 

to  so  with  the  sun  as  far  from  the  meridian  as  practicable,  for  the  following 
reasons : 

It  is  only  when  the  sun  is  in  the  pole  of  the  meridian  that  it  has  its  maximum 
efficiency  in  pointing  out  the  direction  of  the  meridian. 

Hence  a  large  hour-angle,  and  a  small  declination,  are  conducive  to  the  elimination 
of  errors  resulting  from  an  incorrect  latitude. 

Indeed,  with  the  sun  precisely  in  the  pole  of  the  meridian,  the  meridian  is  deter- 
mined independently  of  latitude. 

(9.)  In  making  the  several  adjustments,  or  rather  in  verifying  them,  the  student 
should  have  a  true  meridian  established  by  some  other  means  than  by  the  "  solar 
transit,"  as  from  the  North  Star,  by  some  of  the  methods  given  in  works  on  surveying. 
He  should  compare  the  results  of  his  observations  with  this  meridian  at  different 
times  in  the  day,  and  under  different  states  of  the  atmosphere,  till  he  has  learned  any 
peculiarity  of  the  instrument  and  the  utmost  precision  obtainable  with  it,  as  well  as  the 
ordinary  limit  of  non-precision, 

NOTE. —  The  great  utility  of  this  auxiliary,  or  level  attachment,  is  seen  in  the  setting  of  grades.  Two  of 
these  levels  being  applied  to  the  telescope  of  a  pivot-levelling  instrument  —  one  on  each  side  —  or  one  on  each 
«nd  of  the  cross-axis  of  a  transit  telescope,  and  one  of  them  being  adjusted  to  the  up,  the  other  to  the  down 
,  the  engineer  may  work  in  either  direction  on  his  grade  with  the  same  facility  that  he  would  on  a  level 


c8 

to  dc 


70 


Degree  of  Precision  Required. 

(10.)  This,  of  course,  depends  on  the  character  of  the  work  to  be  done.  In  the 
U.  S.  Public  Land  Surveys, — which  are,  without  question,  conducted  on  the  best  plan 
the  world  can  afford, — only  compass  lines  are  required.  As  a  consequence,  a  wide 
margin  for  non-precision  is  given. 

t  In  sub-dividing  a  block  of  townships,  the  surveyor  in  coursing  a  random  of  6 
miles,  is  required  to  make  his  objective  point  within  3  chains.  Charging  the  half 
of  this  error  to  lineal  measurement,  we  find  the  error  of  coursing  must  be  within  10* 
of  the  true  course. 

(11.  j  In  Manitoba,  the  authorities,  having  fallen  in  love  uith  our  system  of  Pub- 
lic Land  Surveys,  have  adopted  it ;  but  they  require  greater  precision.  They  re- 
quire clear  transit  lines,  projected  with  the  best  six-inch  silver  lined  instruments, 
graduated  to  10". 

In  coursing  a  6  mile  random  in  the  sub-division  of  a  township,  the  surveyor 
must  make  his  objective  point  within  one  chain,  in  order  to  save  reviewing  his  work, 
charging,  as  before,  one  half  of  this  error  to  the  lineal  measurements,  we  find  the 
maximum  error  allowed  in  coursing  to  be  between  3*  and  4'. 

(12)  With  the  "  New  Solar,"  as  manufactured  by  Messrs.  C.  L.  Berger  &  Sons, 
the  surveyor  will  be  surprised  and  delighted  to  see  the  facility  and  certainty  with 
which  he  can  bring  his  work  far  within  the  above  limit. 

Inclination  of  the  Meridian. 

(13.)  In  projecting  arcs  of  a  great  circle  with  the  "solar  transit,"  it  is  of  ths 
utmost  importance  that  the  surveyor  be  able  to  tell  the  inclination  of  the  meridians  for 
any  latitude,  and  for  any  distance  of  eastings  or  westings. 

As  this  problem  is  not  treated  in  elementary  works  on 
surveying,  perhaps  the  few  following  hints  may  be  of  use 
to  the  young  student. 

In  the  following  figure,  let  the  two  arcs  A  G,  and  B  G 
be  two  arcs  of  a  quadrant  of  the  meridian,  1°  of  longitude 
apart.  Let  A  B  =  the  arc  of  one  degree  of  longitude  on 
the  equator  =  69.16  miles. 

Let  D  E  be  an  arc  of  longitude  on  any  parallel  of 
latitude.  Also,  let  E  H  and  D  H  be  the  tangents  of  those 
meridians  meeting  in  the  earth's  axis  produced,  and  cor- 
responding to  the  parallel  of  latitude  D  E. 

Then  the  line  E  F  =  D  F  =  cos  L  =  cos  A  D  or  B  E. 
Also,  the  angle  D  F  E  =  l°,and  the  angle  D  H  E=the 
inclination  of  the  meridians,  which  is  the  angle  we  wish 
to  find,  and  which  we  will  represent  by  X°.  And,  because 
the  two  triangles  F  D  E  and  D  H  E  are  on  the  same  base 
E  D,  and  isosceles,  their  vertical  angles  vary  inversely  as 
their  sides ;  and  we  have  the  equation, 

1°XEF=X°XEH,  But 

E  F  =  cos  L,  and  E  H  =  cot  L,  hence 

X°  cot  L  =  l°  cos  L,  or 

X°  =  cos  L  -4-  cot  L  =  sin  L, (a) 

That  is  to  say, 

The  inclination  of  the  meridians  for  any  difference  of  longitude,  varies  as  the  sine 
of  the  latitude. 

(14.)  Since  the  sine  of  the  latitude  is  the  inclination  in  decimals  of  a  degree,  for 
one  degree  of  longitude,  if  we  multiply  by  3600"  we  shall  have  the  inclination  in 
seconds  of  arc.  Then,  if  we  divide  this  by  the  number  of  miles  in  one  degree  of 
longitude  on  that  latitude,  we  shall  have  the  inclination  due  to  one  mile  on  that 
parallel.  Thus,  for 

Latitude  43° log.  sine  =    9.833783 

Multiply  by  3600" "  =    3.556303 

3.390086 


Divide  by  50™66,  =  1°  long,  on  that  L,  log. 
4S".46  =  inclination  for  one  mile  of  long. 


1.704682 
1.685404 


71 

(15.)  The  use  of  the  Inclination,  as  found  by  the  preceding  article,  is  to  show 
the  surveyor  how  much  he  must  deflect  a  line  of  survey  from  the  due  east  or  west, 
to  have  it  meet  the  parallel  at  a  given  distance  from  the  initial  point  of  the  survey,  — 
for  it  will  be  remembered  that  a  parallel  of  latitude  is  laid  out  as  a  curve  lying  in  a 
horizontal  plane  and  having  the  cotangent  of  the  latitude  for  its  radius.  And  the 
line  due  east  or  west  is  the  tangent  of  the  curve. 

Thus,  on  latitude  43°,  I  wish  to  project  a  six-mile  line  west,  for  the  southerly 
line  of  a  township. 

Remembering  that  in  an  isosceles  triangle,  the  angle  at  the  base  is  less  than  a 
right  angle  by  half  the  angle  at  the  vertex,  I  deflect  my  line  towards  the  pole  by  the 
inclination  due  to  three  miles, — or  in  this  case  48"  .46  X  3  =  2'  .25",  i.  e.,  Deflection 
=  Yz  Inclination. 

(16.)  Table  No.  Ill,  which  was  computed  from  the  formula  (a)  Art.  37,  gives  the 
Inclination  for  one  mile,  and  for  six  miles  on  any  parallel,  from  10°  to  60°  of  latitude; 
also  the  Convergency  for  six  miles,  on  any  latitude. 

(17.)  The  Convergency  of  the  meridian  is  readily  found  for  any  given  distance 
from  the  corresponding  inclination,  by  multiplying  the  Sine  of  the  inclination  by 
the  given  distance. 

Thus,  for  latitude  43°,  the  inclination  for  one  mile  is  4S/'.46;  the  sine  of  which  is 
.000235.  This,  multiplied  by  the  number  of  links  in  a  mile,  which  ==  8000,  we  have 
the  convergency  for  one  mile,=  l.S8  links. 

Multiplying  this  by  the  number  of  miles  in  atownship,=36,  and  we  have  the 
convergency  for  a  township  =  G7.C8  links.  In  this  manner  were  the  convergencies 
of  table  III  computed. 

(18.)  Deflection  of  Mange-Lines  from  meridian.  The  second  column  of  table  III 
shows  the  surveyor  how  much  he  must  deflect  the  range  lines  between  the  several 
sections  of  a  township  from  the  meridian,  in  order  to  make  the  consecutive  ranges 
of  sections  in  a  township  of  uniform  width,  for  the  purpose  of  throwing  the  effects 
of  "convergency"  into  the  most  westerly  range  of  quarter  sections  agreeably  to  law. 
Thus,  say  between  45°  and  55°  of  latitude,  the  inclination  is  practically  1'  for 
every  mile  of  easting  or  westing.  Then,  bearing  in  mind  that  in  the  U.S.,  «»«  sur- 
veys arc  regarded  as  projected  from  the  East  and  South  to  the  West  and  North ;  the 
surveyor  must  project  the  first  range-line  between  the  sections  of  a  township  in  those 
latitudes,  V  to  the  left  of  the  meridian. 

The  second,  2' ;  the  third,  3' ;  and  so  on  to  the  fifth,  which  must  be  6'  to  the  left 
of  the  meridian  on  the  east  side  of  the  township. 

By  this  means  all  the  convergency  of  the  township  is  thrown  into  the  sixth,  or 
westerly  range  of  sections,  as  the  law  directs. 

The  fourth  column  of  the  above  table  shows  the  amount  of  this  convergency. 
This  column  is  also  useful  in  sub-dividing  a  block  of  territory  embraced  by  two 
"standard  parallels"  and  two  "guide  meridians"  into  townships.  Thus,  starting  a 
meridian  from  a  standard  parallel  on  latitude  43°  N,  for  the  western  boundary  ol 
a  range  of  township, — say  the  first  one  west  from  the  guide  meridian, — and  running 
North,  say  4  townships,  the  surveyor  must  make  a  point  that  is  East  of  the  six-mile 
point  on  the  northern  "standard  parallel"  4  X  67.7  links  =  270.8  links,  The  second 
meridian  should  fall  8  X  67.7  links  to  the  right  of  the  twelve-mile  point,  etc. 

(19.)  The  Variation  of  the  Needle.  This  is  easily  determined  by  noting  th« 
reading  of  the  needle  when  the  solar  transit  telescope  has  been  brought  into  th« 
meridian. 


Observation   for   Meridian   with   the    Berger    Solar 

Attachment. 

Written  for  this  catalogue  by  GEO.  L.  HOSMER,  Massachusetts  Institute  of  Technology. 

CALCULATION. 

Before  beginning  the  observations  the  following  computations  must  be  made. 
1.  Take  from  the  Nautical  Almanac  (table  II,  for  the  month)  the  sun's  "apparent 
declination,"  for  Greenwich  Mean  Noon  of  the  date  of  the  observation.  If  it  is 
north  prefix  a  -f  sign,  if  south,  a  —  sign.  2.  On  the  same  line,  in  the  next 
column  to  the  right  is  the  "difference  for  one  hour,"  with  the  proper  algebraic 
sign  before  it.  3.  The  local  time  corresponding  to  Greenwich  Mean  Noon  maj  be 
found  by  subtracting  the  west  longtitude  of  the  place  from  12h,  e.  g.  at  the  ?6th 
meridian,  this  would  give  7h  A.M.;  at  the  90th,  6h  A.  M.,  etc.  4.  Next  compute 
the  declination  for  each  hour  by  adding  algebraically  the  "difference  for  1  h" 
to  the  decimation  for  the  preceding  hour.  6.  Next  correct  each  of  these  declina- 


72 

tions  for  refraction,  using  the  tables  given  in  this  catalogue,  or  such  as  are  given 
in  Prof.  J.  B.  Johnson's  work  on  surveying.  Careful  attention  should  be  paid  to 
signs. 

We  <vill  assume  for  the  present  that  the  latitude  is  known,  and  proceed  to  the 
description  of  the 

FIELD   OPERATIONS. 

1.  Lay  off  on  the  vertical  arc  the  declination  setting  for  the  time  of  observation, 
tipping  the  telescope  in  such  a  direction  that  the  small  telescope  will  point  above 
or  below  the  equator  according  as  the  declination  is  N.  or  S.  2.  Lev<  1  the  small 
telescope  by  means  of  its  attached  level,  and  then  clamp  it.  3.  Next  change  the 
setting  of  the  vertical  circle  so  that  it  reads  the  co-latitude  of  the  place.  5.  Using 
both  tho  horizontal  and  the  equatorial  motions,  point  the  small  telescope  at  the 
sun,  making  the  four  segments  cut  off  by  the  cross  hairs  equal.  The  main  tele- 
scope is  now  in  the  meridian.  To  be  certain  that  the  settings  are  correct  wait  a 
few  moments  and  see  if  the  disc  follows  the  equatorial  wires  perfectly.  Both 
plates  should  be  clamped  while  the  image  is  in  the  center  of  the  field.  The  line 
may  then  be  brought  down  to  the  ground  and  marked. 

EXAMPLE   OF   COMPUTATION. 

Long.  5h.  West.,  Lat.  -f  40°.     Jan.  10,  1900. 
Decl.  for  Gr.  Mean  Noon  =  —  21°  59'  04". 
Diff.  for  Ih.  =  -f  22".25. 

TIME.  DECLINATION.  REFRACTION  SETTING. 

7h.  A.M.  21°  59'  04" 

8  58  42  5'  40"  21°  53'  02" 

9  "  58  20  2'  51'  21   55   29 

10  "  57  57  2' 07"  21    55  50 

11  «  67  35  1'  51"  21    55  44 

12  M.  57  13  (!'  47")  (21    55   26) 

1  P.M.  56  51  1'  51"  21    55  00 

2  "  56   28  2'  07"  21    54  21 

3  "  56  06  2'  51"  21    53   15 

4  "  55  44  5'  40"  21    50  04 

The  co-latitude  may  be  found  by  measuring  the  altitude  of  the  sun's  lower 
limb  at  noon,  i.e.  by  measuring  the  maximum  altitude.  This  angle  must  be  cor- 
rected for  refraction,  semi-diameter  and  declination.  The  result  is  the  co  latitude. 
The  co-latitude  may  also  be  found,  very  nearly,  as  follows:  —  Make  the  angle  be- 
tween the  t  elescopes  equal  to  the  declination  setting  at  noon  in  the  same  way  as  for 
any  other  hour.  Bring  the  telescopes  into  the  same  vertical  plane,  and  point  the 
small  telesoope  at  the  sun.  By  varying  the  elevation  angle  of  the  main  telescope 
keep  the  small  telescope  pointing  at  the  sun  until  a  maximum  elevation  is  reached. 
This  angle  is  the  co-latitude,  already  corrected  for  refraction,  semi-diameter  and 
declination.  This  method  is  not  quite  as  accurate  as  the  former. 

A  TEST. 

The  following  observations  were  made  by  the  writer  with  the  Berger  Solar 
Attachment.  The  plates  were  clamped  at  zero  degrees  and  the  meridian  found  by 
solar  observation.  An  angle  was  then  turned  to  a  mark  *^  mile  away.  The  re- 
sults are  as  follows :  — 

TIME.  Az.  ANGLE 

A  M. 

8:30  240°  07' 

8:40 
8 :50 

9 :00  06 

P.M. 

3:23  240°  05' 

3 :30  03 

Clouds  prevented  further  observations. 

The  true  azimuth  as  found  afterward  by  an  observation  on  Polaris  was  240°  05' 
30". 


73 

Table  I. 

Mean  Refraction  of  Celestial  Objects  for  Temperature  5O°, 
and  Pressure  29*6  inches. 


Alt. 

Refr, 

Alt. 

Refr. 

Alt. 

Refr. 

Alt. 

Refr. 

Alt. 

Refr. 

O     f 

O   O 

'    If 

33  o 

0     f 

5  30 

'    // 

9  8 

o    f 
12   0 

'   tr 

4  23 

0     / 

23  o 

'   If 
2  14 

0     / 

46  o 

'   tf 

0  55 

IO 

31  22 

40 

854 

20 

4  1  6 

20 

2  12 

47  o 

0  53 

20 

29  50 

50 

8  41 

40 

4  9 

40 

2  10 

48  o 

o  5i 

30 

28  23 

6  o 

8  28 

13  o 

4  3 

24  o 

2   8 

49  o 

o  49 

40 

27  o 

10 

S  15 

2O 

3  57 

20 

2   6 

5°  ° 

o  48 

5° 

25  42 

20 

8  3 

40 

3  5* 

40 

2  4 

51  ° 

o  46 

I   0 

24  29 

3° 

7  51 

14  o 

3  45 

25  o 

2   2 

52  o 

o  44 

10 

23  20 

40 

7  4° 

20 

3  4o 

20 

2   0 

53  o 

0  43 

20 

22  15 

50 

7  3° 

40 

3  35 

40 

1  58 

54  ° 

o  41 

3° 

21  15 

7  o 

7  20 

15   0 

3  30 

26  o 

I  56 

56  o 

o  38 

40 

20  18 

IO 

7  'I 

20 

3  26 

20 

i  55 

58  o 

o  35 

50 

'9  25 

20 

7  2 

40 

3  21 

40 

i  53 

60  o 

o  33 

2   0 

1835 

30 

653 

16  o 

3  17 

27  o 

i  5i 

62  o 

o  30 

IO 

1748 

40 

645 

20 

3  12 

3° 

i  49 

64  o 

o  28 

2O 

'7  4 

50 

637 

40 

3  8 

28  o 

i  47 

66  o 

o  25 

30 

1  6  24 

8  o 

6  29 

17  o 

3  4 

30 

i  45 

68  o 

o  23 

40 

'5  45 

10 

6  22 

20 

3  i 

29  o 

i  42 

70  o 

0  21 

5° 

'5  9 

20 

6  15 

40 

2  57 

3°  ° 

i  38 

72  o 

o  18 

3  o 

H36 

30 

6  8 

18  o 

2  54 

31  o 

'  35 

74  o 

o  16 

10 

14  4 

40 

6  i 

20 

2  51 

32  o 

1  31 

76  o 

o  14 

20 

'334 

50 

5  55 

40 

2  47 

33  o 

i  28 

78  o 

0  12 

3° 

13  6 

9  o 

548 

19  o 

2  44 

34  o 

i  24 

80  o 

0  10 

40 

12  40 

IO 

5  42 

20 

2  41 

35  o 

I  21 

82  o 

o  8 

50 

12  15 

20 

536 

40 

2  38 

36  c 

i  18 

84  o 

0   O 

4  o 

'I  51 

3° 

5  3i 

20   O 

2  35 

37  ° 

i  16 

86  o 

o  6 

10 

II  29 

40 

5  25 

20 

2  32 

38  o 

i  13 

88  o 

0   2 

20 

ii  8 

5° 

5  20 

40 

2  29 

39  o 

I  10 

90  o 

0   0 

3° 

10  48 

10   0 

5  i5 

21   O 

2  27 

40  o 

i  8 

40 

10  29 

20 

5  5 

20 

2  25 

41  o 

i  6 

5° 

10  II 

40 

4  56 

40 

2  23 

42  o 

i  3 

5  ° 

9  54 

II   O 

4  47 

22   O 

2  20 

43  o 

i  i 

'10 

93S 

20 

4  39 

20 

2  l8 

44  ° 

0  59 

20 

9  23 

40 

4  3i 

40 

2  IO 

45  o 

o  57 

74 


Correction  to  the  Mean  Refraction  given  in  the 
preceding  Table. 


& 

Height  of  the  Thermometer. 

20° 

24° 

28° 

32° 

36° 

40; 

44; 

52° 

56° 

60° 

K 

68° 

72; 

76° 

,8cC 

0      0 

2   40 

2    18 

1  55 

i  33 

I    II 

51 

3l" 

+'' 

10 

IO 

29 

// 
48 

/        // 

*  7 

'  .  " 

1  25 

143 

2      I 

219 

0    20 

2    25 

2    5 

i  44 

i  24 

1    4 

46 

28 

9 

9 

26 

44 

i  i 

117 

133 

I49 

205 

o  40 

2    II 

i  53 

1  34 

i   16 

58 

42 

25 

8 

8 

24 

39 

55 

I   10 

I24 

138 

153 

I       0 

1  59 

1  43 

i  25 

r     9 

53 

38 

23 

8 

7 

21 

36 

5° 

1    3 

117 

130 

M3 

I   20 

i  48 

1  33 

i  17 

1     3 

48 

34 

21 

7 

6 

19 

33 

45 

57 

1    9 

I  21 

i  33 

1  40 

i  39 

i  25 

i  ii 

57 

44 

31 

18 

6 

6 

18 

30 

41 

52 

1    4 

1  '5 

125 

2.      0 

1  31 

i  18 

1     5 

53 

39 

29 

17 

6 

5 

16 

27 

37 

48 

58 

i    8 

i  18 

•3 

i  ii 

i     i 

51 

41 

32 

22 

J3 

^ 

4 

'3 

21 

3° 

38 

46 

54 

i    i 

4    o 

58 

49 

41 

33 

26 

18 

ii 

4 

4 

10 

17 

24 

31 

37 

44 

5° 

c     o 

48 

35 

28 

22 

16 

9 

3 

3 

9 

H 

20 

26 

31 

36 

40 

6    o 

35 

30 

24 

19 

'3 

8 

3 

2 

7 

12 

17 

22 

26 

31 

35 

7    o 

36 

31 

26 

21 

16 

12 

7 

2 

2 

6 

10 

H 

'9 

23 

27 

31 

8    o 

32 

27 

23 

19 

15 

10 

6 

2 

2 

5 

9 

16 

20 

24 

27 

9    ° 

28 

24 

20 

16 

'3 

9 

5 

2 

2 

5 

8 

ii 

'4 

18 

21 

24 

10      0 

26 

22 

18 

15 

12 

8 

5 

2 

4 

7 

10 

13 

16 

19 

22 

12 

21 

18 

15 

13 

10 

7 

4 

I 

4 

6 

9 

ii 

13 

16 

18 

H 

18 

16 

13 

ii 

8 

6 

4 

I 

3 

5 

7 

9 

ii 

M 

16 

16 

16 

J  A 

12 

9 

7 

5 

3 

I 

3 

5 

6 

8 

IO 

12 

H 

18 

M 

12 

10 

8 

6 

5 

3 

I 

2 

4 

6 

7 

9|    10 

12 

20 

'3 

II 

9 

7 

6 

4 

2 

I 

2 

4 

5 

6 

8 

9 

ii 

25 

10 

8 

7 

6 

5 

3 

2 

I 

2 

3 

4 

5 

6 

7 

8 

3° 

8 

7       6 

5 

4 

3 

2 

I 

O 

I 

2 

3 

4 

5 

6 

7 

35 

7 

6}      5 

4 

3 

2 

I 

0 

0 

I 

2 

3 

3 

4 

5 

6 

40 

6 

5 

4 

3 

3 

2 

I 

0 

0 

I 

2 

2 

3 

3 

4 

5 

45 

5 

4 

3 

3 

2 

2 

I 

0 

o 

I 

I 

2 

2 

3 

3 

4 

5° 

4 

3 

3 

2 

2 

I 

I 

o 

0 

I 

I 

2 

2 

2 

3 

3 

55 

3 

3 

2 

2 

2 

I 

I 

0 

0 

I 

I 

I 

2 

2 

2 

3 

60 

3 

2 

2 

2 

I 

I 

I 

0 

o 

O 

I 

I 

I 

2 

2 

2 

65 

2 

2 

2 

I 

I 

I 

O 

0 

o 

0 

I 

I 

I 

I 

2 

2 

7° 

2 

I 

I 

I 

I 

I 

0 

0 

o 

0 

0 

I 

I 

I 

I 

I 

80 

I 

I 

I 

0 

0 

O 

0 

o 

o 

0 

O 

0 

0 

I 

I 

I 

9° 

O 

0 

0 

0 

0 

0 

0 

0 

o 

0 

o 

0 

0 

0 

0 

O 

Height  of 

28-26 

2856 

28-85 

29-15 

29'45 

29  '75 

30.05 

30.35 

30*64 

30-93 

Barometer. 

ioobe,. 

inchei. 

inches. 

inches. 

Incfaei. 

inchti. 

inch*.. 

EXAMPLE  1. 

What  is  the  correction  for  refraction  for  an  altitude  of  8°  5',  the  thermometer 
standing  at  50-0°  and  the  barometer  at  29-6°  inches? 

Answer  (by  inspection) 6'  25"  : 

and  therefore, 

Apparent  altitude  . .        . .  —        8°  5' 

Refraction  =      —  6  25" 


True  altitude          7  58  35 

EXAMPLE  II. 

What  is  the  correction  for  refraction  for  the  same  altitude,  the  thermometei 
standing  at  44°  and  the  barometer  at  29-45  inches? 

'    // 

Thermometer  correction  for  altitude  8°  5'  =        -\-  ()    6 
Barometer  ditto  =       —  0    2 


Correction  for  both  is =        -f-  0    4 

Mean  Refraction  =        —  6  25 


.-.True  refraction =        — 621 

o      /      // 

Apparent  Altitude  =-•        850 

True  refraction  =        —  C  27. 


True  altitude  . .        ,  <        . .  1  £8  ?0 


76 


Table   H. 


Coefficients  showing  the  per  cent,  of  Refraction  to  be  applied 
to  the  Sun's  Declination. 


Hours  from  the  Meridian, 

Hours  from  the  Meridian. 

Lat. 

1  H. 

2  H. 

3  H. 

4  H. 

5  H. 

6  H. 

Lat. 

1  H. 

2  H. 

3  H. 

4  H. 

5  H. 

6  H. 

0 

0 

IO 

56 

33 

24 

20 

18 

'7 

36 

94 

82 

71 

64 

60 

59 

12 

63 

39 

28 

24 

22 

21 

38 

95 

85 

74 

67 

63 

62 

H 

69 

45 

33 

27 

25 

24 

40 

95 

87 

77 

70 

65 

64 

16 

74 

5o 

38 

3l 

29 

28 

42 

96 

88 

79 

72 

68 

67 

18 

78 

55 

42 

35 

32 

31 

44 

96 

89 

Si 

74 

7i 

69 

20 

81 

60 

46 

39 

35 

34 

46 

97 

90 

83 

77 

74 

72 

22 

84 

64 

5° 

42 

38 

37 

48 

98 

91 

85 

79 

76 

74 

24 

87 

08J54 

46 

42 

41 

5° 

98 

92 

86 

Si 

78 

76 

26 

89 

70 

57 

49 

45 

44 

52 

98 

93 

88 

83 

Si 

79 

28 

90 

72 

60 

5i 

48 

47 

54 

99 

94 

90 

85 

83 

81 

3° 

91 

74 

63 

54 

5i 

5o 

56 

99 

95 

91 

87 

85 

83 

32 

92 

77 

66 

57 

54 

53 

58 

99 

96 

92 

ss 

86 

85 

34 

93 

80 

69 

61 

57 

56 

60 

99 

97 

93 

90 

88 

87 

For  the  construction  of  the  above  table,  see  p.    67. 


77 


Table 
Inclination  and  Convergency  of  the  Meridians. 


Lat. 

Inclina- 
tion for 
one  mile. 

Inclina- 
tion for 
six  miles 

fill 

mi 

8    2" 

Lat. 

Inclina- 
tion for 
one  mile. 

Inclina- 
tion for 
six  miles 

Convergencyl 
for  one 
township  of  1 
36  miles.  | 

Lat. 

Inclination 
for  one  mile. 

Inclina- 
tion for 
six  miles 

Conver^ency 
for  one 
township  of 
36  miles. 

0 

10 

II 
9.18 

'     // 

55 

LINKS. 
I3.0 

o 
27 

if 
26.52 

f      It 
239 

LINKS. 
36.9 

o 

44 

'       It 
50.19 

'     // 
501 

LINKS. 
70.1 

II 

10.13 

I  01 

14.2 

28 

27.66 

2  46 

38.6 

45 

52.00 

5I2 

72.6 

12 

II.07 

1  06 

15-5 

29 

28.85 

253 

40.2 

46 

53.83 

523 

75.2 

'3 

I2.O2 

I    12 

16.8 

3° 

3°-°3 

300 

41.9 

47 

55^7 

534 

77.8 

H 

12.98 

i  18 

iS.i 

3* 

31,26 

307 

43-6 

48 

57^7 

546 

80.6 

i5 

13.96 

i  24 

19.4 

32 

32.49 

315 

454 

49 

59^3 

559 

83.5 

16 

H-93 

i  30 

20.7 

33 

33-83 

323 

47.2 

5° 

I   O2.OO 

6  12 

86.5 

'7 

15.92 

i  36 

22.0 

34 

35-I7 

33r 

49.1 

5* 

I  04.17 

6  25 

897 

18 

16.91 

141 

23'4 

35 

36-50 

339 

5°«9 

52 

I  06.67 

6  40 

93-° 

J9 

17-93 

147 

24.9 

36 

37-83 

346 

52.7 

53 

I   09.17 

655 

964 

20 

18.94 

1  54 

26.5 

37 

39-17 

355 

54-7 

54 

I    16.67 

7  10 

1  00.0 

2J 

19.98 

2  OO 

27.8 

38 

40.67 

404 

56.8 

55 

1  H-33 

7  26 

103.7 

22 

21.02 

2  06 

29-3 

39 

42.17 

4i3 

58.8 

56 

i  17.17 

743 

107.6 

23 

22.10 

213 

30.8 

40 

43-67 

4  22 

60.9 

57 

I   20.00 

8  oo 

1  1  1.8 

24 

23-J7 

2  19 

32-3 

41 

45-i7 

431 

63.1 

58 

I   22.00 

8  19 

116.2 

25 

24.30 

2  26 

33-8 

42 

46-85 

441 

65.4 

59 

I   26.66 

840 

120.9 

26 

25-38 

232 

35-4 

43 

48.52 

451 

67.7 

60 

I  30.00 

9  oo 

125.7 

For  the  construction  and  use  of  the  above  table,  see  articles  (13,)  (14,)  (15,) 
(17.)  (18,)  page  70. 

For  details  of  instruction  in  U.  S.  Government  Surveying,  see  Hawes'  System 
of  "Rectangular  Surveying,"  and  Burt's  "Key  to  Solar  Compass." 


78 

To  Find  the  Meridian  from  "  Polaris." 

The  north  star,  Polaris,  being  out  of  the  pole  of  the  equator,  is  in  the  meridian  but 
twice  in  a  stellar  day  —  once  above  and  once  below  the  pole  —  called  the  upper  and 
lower  transits,  or  culminations. 

It  is  also  at  its  extreme  distance,  east  and  west,  twice  in  a  stellar  day,  called 
greatest  elongations,  east  or  west. 

At  the  time  of  a  culmination,  it  would  be  only  necessary  to  get  the  bearing  of  the 
star  to  have  the  place  of  the  true  meridian.  But  this  would  require  an  exact  knowl- 
edge of  the  time,  an  element  not  usually  possessed  by  surveyors.  Moreover,  the 
observation  must  be  made  with  certainty,  at  the  instant,  which  is  not  always  practi- 
cable. On  this  account,  this  method  is  not  in  favor  with  surveyors. 

At  elongation,  the  apparent  motion  of  the  star  is  tangent  to  the  vertical,  and 
therefore,  for  a  few  minutes,  with  regard  to  azimuth,  it  appears  to  stand  still,  thereby 
Wording  ample  time  for  deliberate  observation. 

The  distance  of  thrs  star  from  the  pole-  called  its  polar  distance,  was  1°  18'  16" 
on  January  1,  1885,  and  is  diminishing  at  the  rate  of  about  19.06"  per  year,  whence 
its  distance  in  following  years  may  be  known.* 

The  azimuth  of  the  star,  corresponding  to  any  polar  distance,  is  variable  with  the 
latitude.  Thus,  an  observer  at  the  equator  would  see  this  star  —  say  at  eastern 
elongation  —  in  the  horizon,  and  at  the  distance  of  1°  18'  16"  to  the  right  of  the  pole, 
or  true  meridian. 

If  now  the  observer  should  go  north,  the  azimuth  of  the  star  would  increase  with 
its  altitude,  till  he  should  arrive  at  a  latitude  equal  to  the  complement  of  the  polar 
distance,  when  it  would  be  N.  90°  E.  Between  these  limits,  the  bearing  of  the  st?,r, 
at  elongation  from  the  pole,  would  vary  according  to  the  following  equation,  in  which 
Z  =  the  azimuth,  or  bearing  : 

„.    7  _  sin  Polar  Distance 
:    cosine  Latitude 

As  the  telescope  of  the  surveyor's  transit  is  not  usually  of  sufficient  power  to  show 
the  star  in  the  daytime,  the  observation  must  be  made  at  night,  in  which  case  the 
cross-wires  of  the  telescope  must  be  illuminated  by  light  reflected  into  the  tube.  A 
piece  of  stiff  white  paper,  with  an  opening  large  enough  to  admit  of  seeing  the  star 
through  it,  and  held  obliquely  in  front  of  the  telescope,  will  make  a  good  reflector. 

As  generally  but  one  of  the  elongations  can  be  seen,  on  the  same  night,  it  is  im- 
portant to  know,  which  one  is  observed.  Also  the  latitude  must  be  known,  at  least 
approximately. 

The  pole  is  nearly  in  line  between  Polaris  and  the  star  Mizar,  which  is  at  the  bend 
in  the  handle  of  the  Dipper,  so  that  when  these  two  stars  are  nearly  in  a  horizontal  line 

and  the  dipper  is  ^jjj.  j-  of  the  pole,  Polaris  is  at  his  greatest  elongation  ^J   j-  • 

In  sighting  to  the  star,  the  observer  must  be  careful  to  keep  his  transit  level 
transversely,  for  the  star  is  so  high  that  inattention  to  this  might  introduce  a  serious 
error  into  the  resulting  azimuth. 

A  satisfactory  sight  having  been  obtained,  the  telescope  should  be  brought  down 
to  fix  a  mark  on  the  ground,  at  a  distance  of  300  to  400  yards  from  the  transit. 

This  mark  should  be  something  clear  and  definite,  like  a  nail  set  in  a  hub,  driven 
into  the  ground,  which  may  be  located  by  means  of  a  plummet  lamp,  or  by  means 
of  a  common  lamp  in  a  box,  having  a  vertical  slit  in  one  side  of  say  £  or  f  an  inch  in 
thickness,  with  a  plumb-line  suspended  from  the  slit,  and  manipulated  by  an 
assistant. 

The  direction  of  the  star  being  satisfactorily  marked,  compute  the  azimuth  from 

the  above  equation,  and  set  the  resulting  angle  off  to  the  I1?,.     ]•  of  the  mark  for 


It  may  happen,  that  the  resulting  azimuth  may  have  an  odd  number  of  seconds, 
or  fraction  of  a  minute,  not  convenient  to  be  set  off  with  a  vernier  graduated  to 

*  Small  corrections  to  the  distances  thus  calculated  are  needed,  but  do  not  amount  to  more  than  30"  IB 
all  ;  see  a  Nautical  Almanac. 


79 


single  minutes.     In  this  case,  find  the  distance  carefully  between  the  transit  and  the 
mark,  and  multiply  this  distance  by  the  tangent  of  the  azimuth.    The  result  set  off 

to  the  j*1??1*1  }  for  ^estle™  [  elongation,  will  point  out  the  place  of  the  true  meridian. 


left    ( iv/i  eastern 


Meridian  from  Equal  Altitudes  of  the  Sun. 

If  the  direction  of  a  star  were  observed  with  a  transit  when  it  had  a  certain  altitude 
on  the  easterly  side  of  the  meridian  and  the  direction  again  observed  when  it  had  an 
equal  altitude  on  the  westerly  side,  then  the  bisector  of  the  angle  would  give  the  direc- 
tion of  the  meridian. 

If  these  observations  are  made  on  the  sun  an  allowance  must  be  made  for  the  slight 
change  in  the  sun's  declination  between  the  two  observations.  From  about  Decem- 
ber 21  to  about  June  21  the  sun  is  going  north  and  from  June  21  to  December  21  it  is 
going  south.  The  table  given  below  shows  the  number  of  seconds  the  sun  moves  in  1 
hour  on  different  days  in  the  year. 

To  an  observer  in  north  latitude,  when  the  sun  is  going  north,  the  mean  of  the  two 
vernier  readings  would  lie  to  the  west  of  south  ;  if  the  sun  is  going  south  the  mean 
would  lie  east  of  south.  The  correction  to  the  mean  of  the  vernier  readings  is  found 

by  the  formula  ; — : —     In  this  formula  D  is  the  total  increase  or  decrease  in 

2  cos  <p  sin  t. 

the  sun's  declination  between  the  two  observations  ;  <£  =  the  latitude ;  t  =  the  hour 
angle,  or  very  nearly  i  the  elapsed  time. 

Making  the  Observations. 

1.  In  the  forenoon,  set  up  the  transit,  with  the  vernier  set  at  0°.    Point  at  some  ob- 
ject for  an  azimuth  mark,  preferably  at  the  left  of  the  sun,  using  the  lower  clamp  and 
tangent  screw. 

2.  Loosen  the  upper  clamp  and  point  the  telescope  toward  the  sun  and  find  the 
sun's  image  in  the  field.     Move  the  telescope  slightly  until  the  vertical  and  horizontal 
wires  are  found.     The  beginner  is  cautioned  against  mistaking  a  stadia  wire  for  the 
middle  wire. 

In  the  forenoon  the  sun  is  rising  and  moving  to  the  right.  If  the  telescope  has  an 
inverting  eye-piece  these  motions  will  of  course  appear  to  be  reversed.  If  a  prism  is 
used  the  vertical  motion  will  be  contrary  to  what  it  would  be  without  the  prism,  while 
the  horizontal  motion  will  not  be  affected. 

3.  Set  the  telescope  at  an  altitude  a  little  above  the  sun.     Set  the  vertical  wire  on  the 
left  limb  of  the  sun  and  follow  it  in  azimuth,  using  the  upper  clamp  and  tangent  screw, 
until  the  lower  limb  of  the  sun  just  touches  the  horizontal  wire.     At  this  instant  stop 
following  the  motion  in  azimuth,  note  the  time  by  a  watch  and  then  read  the  vernier. 
It  will  be  well  also  to  read  the  altitude. 

4.  In  the  afternoon  turn  the  telescope  toward  the  sun,  the  altitude  being  the  same  as  at 
the. first  observation.     When  it  comes  into  the  field  set  the  vertical  wire  tangent  to  the 
right  limb  of  the  sun.     Follow  it  in  azimuth  until  the  lower  edge  of  the  sun  again 
touches  the  horizontal  wire.     Note  the  tune  and  read  the  vernier. 

Calculations. 

Take  from  the  table  the  hourly  change  in  declination  for  that  day  and  multiply  by 
the  number  of  hours  and  fraction  of  an  hour  between  the  observations.  The  result  is 
to  be  divided  by  twice  the  product  of  the  cosine  of  the  latitude  by  the  sine  of  the  hour 
angle.  This  gives  the  correction  to  the  mean  of  the  vernier  readings.  The  hour  angle 
is  half  the  elapsed  time  and  should  be  turned  into  degrees  and  minutes  by  multiplying 
by  15.  Take  the  mean  of  the  vernier  readings  and  then  subtract  the  correction  if  the 
sun  is  going  north,  add  if  it  is  going  south.  It  is  assumed  that  the  circle  reads  from  0° 
to  360°  in  a  clockwise  direction. 


80 


REMARKS.  If  the  instrument  is  not  in  a  very  stable  condition  it  will  be  best  to 
re-set  on  0°,  point  at  the  azimuth  mark  again,  and  then  re-set  at  the  proper  altitude  as 
nearly  as  possible,  before  making  the  second  observation. 

The  nearer  the  sun  is  to  the  east  and  west  points  the  better  the  result.  Observa- 
tions near  noon  should  be  avoided.  Observations  at  very  low  altitudes,  say  under  10° 
are  unsatisfactory. 

If  only  approximate  results  are  desired  the  vertical  wire  may  be  made  to  bisect  the 
sun's  disc  in  both  cases.  This  would  avoid  the  mistake  of  getting  the  wrong  limb. 


Date,  April  10. 

Forenoon  observation 
Afternoon         " 


EXAMPLE. 

Latitude  43°  N. 

vernier  A.  Watch  Reading. 

,     .       13°  26'      right  of  mark  7^.  18m. 

"        *'        "  4h.  48m. 


mean 


148°  13' 
80°  49'  30" 


diff.     9k  30m. 


Diff.  lh.  =  54" 
64"  X  9. 6  h.  =513" 
cos<£=    .7314 
sin  t=    .9469 
2  cos  <£  sin  t  =  1.3851 
513 


t  =  4h.  45m. 
=  71°  15 

mean  80°  49'  30" 
corr  6'  10 


1.3851 


=  370."4=6'  10."4 


Angle  between  )   fi      ,„, 

meridian  and  mark   f  * 


Hourly  Motion  of  the  Sun  in  Declination. 


Mo°nth. 

Jan. 

Feb. 

March. 

April. 

May. 

June. 

July. 

Aug. 

Sept. 

Oct. 

Nov. 

Dec. 

„ 

„ 

„ 

„ 

„ 

„ 

„ 

tt 

„ 

tt 

tt 

tt 

I 

+  12 

43 

57 

58 

45 

21 

IO 

38 

54 

58 

48 

23 

5 

17 

46 

58 

56 

43 

17 

H 

41 

56 

58 

46 

19 

10 

22 

49 

59 

54 

39 

12 

19 

44 

57 

57 

42 

14 

15 

28 

52 

59 

52 

36 

7 

24 

47 

58 

56 

38 

8 

20 

32 

54 

59 

49 

3i 

+  2-J 

28 

49 

58 

54 

34 

-21 

25 

37 

56 

59 

47 

27 

-4J 

32 

52 

59 

52 

30 

+  4J 

30 

4i 

58 

46 

23 

9 

36 

54 

59 

49 

'5 

IO 

81 


Transit  Solar  Attachment. 

For  running  Meridian  or  other  lines  by  the  Sun. 

Written  for  tnis  catalogue  with  special  reference  to  the  wants  of  Public  Land  Surveyors,  for  both  common  and 

mineral  lands,  by  J.  B.  DAVIS,  Assistant  Professor  of  Civil  Engineering, 

University  of  Michigan. 

1.  Remarks.  The  attachment  herein  referred  to  is  the  Davis  and  Berger 
solar  screen,  prism,  and  colored  shade  glass,  used  for  direct  solar  observation. 
These  inventions  have  been  devised  by  the  Mr.  Berger,  of  the  firm  of  C.  L.  Berger 
&  Sons,  and  by  the  writer.  They  are  simply  for  the  purpose  of  enabling  one 
to  make  an  observation  directly  upon  the  sun's  centre.  This  observation  being 
secured  by  readings  of  the  horizontal  and  vertical  circles,  is  reduced  so  as  to 
give  the  direction  of  the  line  of  sight  of  the  transit  at  the  instant  of  the  observa- 
tion. Thus  knowing  the  direction  of  the  line  of  sight  at  a  given  instant  it  becomes 
simply  necessary  to  turn  off  the  angle  which  this  line  of  sight  makes  with  the 
meridian,  to  ascertain  the  position  of  the  meridian.  This  angle  is  what  is  obtained 
by  reducing  the  observation,  as  above  mentioned.  A  brief  reference  to  the  history 
of  these  devices  will  best  explain  them.  It  occurred  to  the  writer  to  see  if  an  image 
of  the  sun  could  be  formed  behind  the  eye-piece  of  a  telescope  at  the  same  time 
an  image  of  the  cross-wires  was,  and  the  latter  image  be  made  to  quarter  the 
former,  by  allowing  the  sun  to  shine  into  the  object  end  of  the  telescope  and  thence 
directly  through  it.  The  experiment  was  made  by  holding  a  piece  of  white  paper 
behind  the  eye-piece,  and  adjusting  the  focus  of  the  eye-piece  and  object  glass. 
The  very  first  trial  was  readily  successful.  The  next  thing  was  to  see  if  the  posi- 
tion of  the  instrument  could  be  located  by  this  means  as  near  as  the  circles  would 
read.  By  the  same  simple  means  it  was  soon  found  that  a  motion  given  to  the 
telescope  by  either  tangent  screw  might  be  so  slight  that  the  eye  could  not  detect 
it  upon  the  circles,  but  evidence  of  it  would  be  apparent  in  the  position  of  the  images 
with  reference  to  each  other.  This  fact  at  once  settled  the  question  of  whether 
this  would  be  a  sufficiently  delicate  means  of  observation.  It  showed  that  the 
observations  would  be  closer  than  the  circles  would  read.  After  some  trials  and 
some  months  rest  these  facts  were  brought  to  the  notice  of  others,  and  finally  were 
submitted  to  Mr.  Berger  for  his  opinion.  He  made  a  screen  \vhich  the  writer 
exhibited  at  the  first  annual  convention  of  the  association  of  Michigan  Engineers 
and  Surveyors  at  Lansing.  The  matter  was  further  studied  by  Mr.  Berger.  The 
screen  was  much  improved,  and  the  mechanical  construction  of  it  brought  to 
the  standard  of  the  work  done  by  this  firm.  Mr.  Berger  soon  conceived  the 
idea  of  making  the  screen  of  ground  white  glass  in  a  brass  frame,  as  shown  in 
figs.  1  and  2,*so  one  might  observe  the  position  of  the  images  directly  upon  it, 
and  thus  secure  not  only  the  comfort  of  an  easy  position  in  observing,  but  the 
consequent  accompanying  accuracy.  The  arm  of  attachment  was  perfected  from 
time  to  time.  The  screen  of  ground  glass  is  mounted  upon  an  arm  that  admits  of 
all  adjustments  of  position,  and  is  so  attached  to  the  side  of  the  telescope  tube  that 
it  can  be  turned  up  out  of  the  way  when  not  needed.  The  reflecting  prism 
can  be  screwed  on  to  the  eye-piece  cap  for  observing  at  high  altitudes.  This  also  is 
adjustable  so  as  to  look  in  any  desired  direction  from  the  telescope  tube.  The 
diagonal  eye-piece  also  has  its  movable  colored  shade  glass  as  above  stated.  With 
these  attachments  observations  on  the  sun  at  all  altitudes  may  be  made  in  two 
ways.  By  looking  directly  at  it  through  the  simple  colored  glass  for  low  altitudes, 
or  through  the  prism  and  its  shade  glass  for  high  altitudes.  The  other  way  is  to 
receive  on  the  screen  the  images  of  the  cross-wires  and  the  sun  and  make  the  image 
of  the  cross-wires  just  quarter  the  image  of  the  sun  by  means  of  the  slow  motion 
screws  to  the  circles  of  the  instrument.  For  this  method  the  colored  shade  glasses 
are  not  to  be  used.  With  this  complete  outfit  one  may  work  whichever  way  seems 
bwst. 

*  For  Figures  1,  2,  3,  4,  5,  6  and  7  see  page  175. 


82 

These  devices  are  being  more  and  more  perfected,  and  will  be  protected  by  letters 
patent,  and  Messrs.  C.  L.  Berger  &  Sons  make  and  sell  them  exclusively. 

2.  Rem  irks.     Certain  precautions  are  necessary  in  the  use  of  this  method 
of  finding  the  true  direction  of  a  line  as  well  as  in  any  other.    It  is  not  wise  to 
observe  the  sun,  read  the  circles,  note  clown  the  readings  and  leave  the  instrument 
standing  there  while  making  the  reductions.    It  will  get  out  of  place  in  some  way, 
very  likely.     Therefore,  as  soon  as  the  observation  is  completed  and  the  readings 
of  the  circles  noted,  set  the  line  of  sight  on  some  fixed  point  and  read  the  plate 
again,  noting  this  reading.     Of  course  the  two  plate  readings  will  give  the  horizon- 
tal angle  from  the  sun  to  the  line.    This  will  enable  the  observer,  after  finding  the 
direction  of  the  line  of  sight  when  set  on  the  sun,  to  readily  ascertain  its  direction 
as  set  on  the  fixed  point  referred  to,  thus  determining  the  direction  of  the  line  from 
the  point  over  which  the  instrument  is  set  to  the  fixed  point.     This  line  may  be 
chosen  before  beginning  the  observation,  and  become  the  reference  line  for  the 
work  in  hand. 

3.  Remarks.     For  the  purposes  of  reduction  the  process  by  equations  is 
used  instead  of  one  by  rules.    The  introduction  of  symbols  and  signs  is  a  much 
simpler  matter  than  many  suppose.     It  is  nothing  but  this.    We  agree  that  a  char- 
acter of  some  sort  or  other  shall  represent  a  certain  thing  and  nothing  else. 
Whenever  this  character  occurs,  therefore,  it  simply  means  the  thing  we  have  set 
it  for.    That  is  all  there  is  of  symbolical  representation.    These  very  words  here 
printed  are  all  symbols.    The  method  is  universal.     We  here,  as  elsewhere  in 
algebraic  processes,  make  a  special  application  of  it.    The  rules  for  a  case  of  this 
kind  would  be  very  cumbersome  and  give  the  user  far  more  trouble  than  will  be 
necessary  for  mastering  the  few  equations  given  below.     The  record  of  the  pro- 
cesses is  hereby  reduced  to  a  few  lines,  and  one  has  not  to  go  searching  through  s» 
page  for  a  point  here  and  there,  but  places  his  eye  at  once  upon  what  he  wants, 
where  all  will  be  found  in  a  compact  form.     Of  course  one  needs  to  read  each  word 
and  each  sign.     Nothing  must  be  slurred  over  or  missed.     The  record  as  set  forth 
below  is  exact,  complete  and  reliable. 

4.  Remarks.     All  computations  should  be  thoroughly  checked,  and  check 
equations  and  devices  are  given.    These  should  always  be  applied,  without  fail,  as 
no  one  can  implicitly  trust  a  computation  by  a  single  process,  unrepeated,  even  if 
simple.    No  one  sljould  who  is  a  surveyor  or  engineer.     Several  checks  are  given. 
One  used  is  sufficient,  usually.    If  one  distrusts  the  check  because  it  shows  th« 
work  to  be  wrong,  it  may  be  of  some  satisfaction  to  use  another  or  more  than  one. 

5.  Remarks.    The  directions  prepared  below  are  intended  for  use,  word  by 
word,  and  step  by  step.      It  is  hoped  that  they  will  prove  in  convenient  form  for 
use  as  a  chart  to  direct  the  efforts  of  the  observer  in  his  first  use  of  these  attach- 
ments and  this  method.    Therefore,  it  is  thought  that  one  may  safely  do  as  told, 
trusting  the  next  step  to  the  next  statement.     They  have  been  prepared  with  this 
view. 

6.    Using  the  Screen. 

a.  Directions.    Set  the  instrument  so  the  sun  can  shine  in  at  the  object  end 
of  the  telescope,  and  directly  through  it.    Run  put  the  eye-piece  and  adjust  the 
screen  behind  it,  by  its  sliding  arm,  so  that  a  distinct  image  of  the  cross-wires  can 
be  seen  on  the  screen  within  the  lighted  spot  made  by  the  shining  sun,  as  shown 
in  fig.  2.    Set  the  object  glass  so  as  to  clearly  define  the  image  of  the  sun  on  the 
screen.    Repeat  these  trials,  and  adjust  the  parts  of  the  telescope  and  screen  so 
that  the  clearest  image  of  both  the  cross-wires  and  the  sun  will  be  obtained  that 
the  telescope  will  give.     Mark  the  slide  on  the  arm  of  the  screen  and  the  eye-piece, 
so  they  can  be  easily  set  thereafter  for  an  observation. 

b.  Remarks.    The  eye-piece,  when  all  is  in  exact  position,  will  be  found  to 
be  considerably  farther  out  than  for  an  ordinary  sight.     The  marking  of  the  sliding 
arm  and  eye-piece  will  save  time  in  ths  future.    These  trials,  when  made  with  a 
new  apparatus,  should  be  conducted  at  leisure  and  with  extra  care,  for  the  purpose 
of  fitting  the  apparatus  carefully  to  the  telescope.    A  few  trials  may  be  needed  at 
first  in  order  to  accustom  the  observer  to  recognize  the  best  definition  of  the  images. 

This  solar  screen  is  especially  adapted  to  the  ordinary  surveyors'  and  engineers' 
transit  telescopes,  with  erecting  eye-pieces.    It  is  not  adapted  to  be  used  with  invert- 


83 

Ing  or  astronomical  telescopes,  unless  during  an  observation  the  aperture  of  the 
objective  is  cut  down  to  £  inch  diameter,  by  means  of  a  diaphragm  placed  in  front  of 
it,  when  the  image  can  be  seen  as  sharply  defined  as  those  of  the  erecting  telescope; 
or  the  observations  must  be  made  with  the  shade  glasses  and  reflecting  prism  alone. 

7.  Using  the  Colored  Shade  Glass. 

a.  Directions.      Attach  the  colored  glass  shown  in  fig.  4,  to  the  eye-piece, 
to  shield  the  eye  from  the  sun  and  look  directly  at  it,  setting  the  cross-wires  so  as 
to  quarter  it. 

b.  Remarks.      This  will  be  found  entirely  satisfactory  when  the  sun's  alti- 
tude is  so  low  as  to  enable  the  observer  to  bring  his  eye  in  apposition  with  the  eye- 
piece of  the  telescope  with  ease. 

8.  Using-  the  Diagonal  Eye-piece. 

a.  Directions.     Screw  on  the  prism,  as  shown  in  fig.  3,  to  the  end  of  the 
common  eye-piece.    Look  directly  through  the  shade-glass,  if  observing  in  that 
way,  turning  the  prism  either  way  so  as  to  make  it  convenient  to  look  into  it.    If 
any  trouble  is  experienced  in  finding  the  sun  with  it.  let  the  sun  first  shine  through 
the  telescope,  the  colored  shade-glass  being  turned  aside,  till  the  brilliant  light 
perceived  in  the  aperture  of  this  eye-piece  shows  the  telescope  to  be  rightly 
directed.     Cover  the  aperture  with  its  shade-glass  and  proceed. 

b.  Remarks.    By  attaching  the  reflecting  prism  to  the  eye-piece  of  the  tele- 
scope, the  light  is  reflected  at  right  angles  to  the  the  line  of  sight  of  the  telescope, 
and  it  thus  becomes  what  is  termed  a  diagonal  eye-piece. 

This  prism  can  be  used  for  direct  observation  when  the  altitude  of  the  sun  is 
too  great  to  allow  the  eye  to  be  applied  directly  to  the  eye-piece  of  the  telescope, 
and  not  so  ^reat  as  to  bring  the  eye-piece  too  far  over  the  plate,  but  through  this 
range  of  altitudes  the  solar  screen  can  be  used  without  the  prism,  as  shown  in  lig.  2, 
and  it  will  usually  be  found  advantageous  to  do  so. 

Since  the  prism  in  effect  withdraws  the  eye  about  half  an  inch  further  from  the 
eye-piece  of  the  telescope  than  its  natural  position,  that  being  about  the  distance 
traversed  by  the  light  in  passing  through  the  prism,  the  high  magnifying  power 
used  in  C.  L.  Berger  &  Sons'  transit  telescopes  makes  the  use  of  the  reflecting 
prism  for  direct  observation  a  little  awkward,  and  it  will  usually  be  found  more 
satisfactory  when  using  the  prism  to  use  the  solar  screen  with  it. 

9.  Using  the  Reflecting  Prism  and  Solar  Screen  combined. 

a.  Directions.    Attach  the  prism,  and  direct  the  telescope  as  in  8.    Then, 
leaving  the  aperture  of  the  prism  uncovered,  adjust  the  solar  screen  so  as  to  receive 
the  images  of  the  sun  and  the  cross-wires,  as  shown  in  fig.  1. 

b.  Remarks.     For  observing  the  sun  at  high  altitudes  it  will  be  found  that  in 
this,  otherwise  most  difficult  of  all  positions,  the  use  of  the  solar  screen  combined 
with  the  prism  will  enable  the  engineer  to  make  his  observation  with  the  greatest 
ease  and  precision. 

10.  Making  the  Observations. 

a.  Directions.     Direct  the  telescope  to  the  sun,  and  by  means  of  the  slow 
motion  screws,  cause  the  image  of  the  cross-wires  to  exactly  quarter  the  sun's  image. 
Read  both  circles  and  record  the  readings.    Eefer  the  position  of  the  instrument  to 
some  fixed  line,  and  once,  after  the  above  work,  by  another  plate  reading.     Also 
note  and  record  the  exact  instant  of  time  of  the  observation  by  the  watch. 

b.  Remarks.     This  observation  with  the  watch  may  be  used  as  hereafter 
indicated  to  simplify  and  lessen  the  amount  of  work  in  making  the  reductions.    A 
fair  watch  of  ordinary  accuracy  is  sufficient.     The  entire  work  can  be  carried  on 
without  a  watch  at  all,  but  it  takes  some  more  figuring. 

11.  Use  of  the  Nautical  Almanac. 

a.  Remarks.     In  order  to  use  the  observations,  made  as  above  directed,  it 
is  necessary  to  find  the  sun's  apparent  declination  for  the  time  of  observation. 
This  is  done  as  directed  below. 

b.  Conditions.     Let  all  the  algebraic  signs  be  carefully  observed  throughout 
the  work.    Use  the  watch  time. 


84 

c.  Directions.    For  finding  the  Sun's  apparent  declination.    Look  in  the  table 
of  Washington  Solar  Ephemeris  against  the  date  of  the  observation,  and  take  out 
the  following  quantities.    First,  the  sun's  apparent  declination,  with  its  sign,  -j- 
when  N.,  —  when  S.,  from  its  column.     Second,  the  hourly  change,  with  its  sign, 
from  its  column.     Find  from    a  map  or  otherwise,  the   difference  in  longitude 
between  the  place  of  observation  and  Washington,  as  near  as  one-half  hour,  or 
seven  and  one-half  degrees.    This  is  -f-  when  W.  and  —  when  E.  of  Washington. 
Add  to  this  difference  of  longitude  the  time  of  the  observation  from  noon,  this  time 
being  -j-  when  the  sun  is  W.  and  —  when  E.  of  the  meridian.     Multiply  the  hourly 
change  by  this  result,  in  hours^  noting  all  the  signs.    Apply  this  product,  regarding 
its  sign,  to  the  sun's  apparent  declination  as  taken,  from  the  table,  for  the  sun's 
apparent  declination  at  the  time  of  the  observation. 

d.  Example.    Date,  1881— 6— 14.    Hour,  9h— 26m— 24*,  A.M.    Longitude 
about  40  minutes  East  of  Washington,  considered  in  time. 

O's  apparent  declination,  1881  —  6  —  14. 
Washington  mean  noon,  -f  23°    18'    15" 
Hourly  motion,  1" 

Time  of  observation  from  noon,  — 2  hours  30  minutes,  about. 

Longitude  East  of  Washington,  — 40  minutes. 

Total  time  of  correction,  —3  hours  10  minutes,  =  3l/e  hours. 

Amount  of  correction  =  —  3l/6  X  1" = — 22 ^" 

O's  apparent  declination  from  table,  -f-       23°    18'  .  15// 

O's  apparent  declination  at  time  of  observation,  +       23°    17'    53"  nearly, 

12.  Reducing  Observations. 

a.  Conditions.    Let  h'  =  the  sun's  altitude,  as  observed. 

Let  £  =  the  latitude  of  the  place  of  observation. 
Let  6  =  the  sun's  apparent  declination  at  the  time  of  obser- 
vation, found  as  above  directed. 

Let  z'=  the  sun's  observed  zenith  distance. 
Let  z  =  the  sun's  true  zenith  distance,  always  -f. 
Let  k  and  A/  be  two  auxiliary  angles  used  in  the  reductions. 
Let  A  =  the  azimuth  of  the  line  of  sight  of  the  instrument  at  the  instant  of  the 
observation,  reckoned  from  the  N.  point  of  the  horizon,  either  E.  or  W.  as  the  sun 
is  E.  or  W.  of  the  meridian. 

Let  t  =  the  sun's  apparent  hour  angle  at  the  time  of  the  observation,  that  is  the 
local  apparent  time  from  apparent  noon  plus  the  change  in  the  sun's  right  ascension 
between  apparent  noon  and  the  time  of  the  observation.  This  is  -{-  when  W.  and 
—  when  E.  of  the  meridian,  or  -j-  for  P.M  ,  and  —  for  A.M.  times.  The  mean  or 
watch  time  is  sufficient  for  use  in  2. 

Let  p  =  an  auxiliary  angle  used  in  some  of  the  reductions. 
Let  all  signs  be  faithfully  regarded.    Let  logarithms  be  used. 

b.  Directions.     For  finding  z  from  z' .     Use  the  following  equations. 

*'=90°  —  /?' (1) 

z  =    z'  +  55"  tan  z' (2) 

C.     Directions.     For  finding  A  when  0, 6  and  z  are  given. 

Find  tan  ^  (k— fc')  =  cot  ^  O~H)  tan  ^  O— <T>  cot  ^  z        .  (3) 

When  ^<<J  and  of  the  same  name  find  k  =  y2  z  -}- %  (k~  *0         '•        •  (4) 

When  ^>d  and  of  the  same  name  find k'=y2  z~y2  (k  —  A;')  .        .  (5) 

When  <p  and  6  have  different  names  find  kf  =*4  z  —  }4  (k  —  A/)  .        .  (6) 

Then  find  A  from  Cos  A  =  tan  k  tan  ^>  or  tan  V  tan  <j>         .        .        .        .  (7) 

Checks. 

When  (4)  is  used  »L*= (8) 


85 

.......       (10) 


Sin  0      Sin 


Find  Sin  p  =  sin  A  cos  0       ......      (12) 

Sin  p  and  cos  p  are  at  the  same  place  in  the  table. 
d.    Example.         <j>  =  42°  16'  30"  N.  *  =  52°  43'  30" 

6  =  18°  13'  20"  N.        £  z  =  2G°  21'  45" 


Checks* 


—  (5  =  24°   3'  10" 
H)=30°14'55" 

—  d)=12°    1'35" 


=  0.2342195  Tan  <fr  =  9.9586273.  Sin  0  =  9.8278148  Cos  6  =  9.8691875 
—  rf)  =  9.3284570  —  Tan  fr=  9.2477939.  Cos  A;'  =9.  9933068  Sin  1=9.9943079 
Cot  y2  z  =0.3048785—  Cos  A=  9.2064212.  Cos  ;>  =  £8345080  Sin  »  =  9~8634954 
Tan  %(*—  jf)=  9.8675550  3894.  <  -  ,  - 

346  318.  At  same  place  in  table. 

204  A  =  99°15'22"5 

%  (k  —  k'}  =  36°  23'  45''  Sin  0  =  9.8278148        Cos  V  =  9.9933061* 

y2  z  =26°  21  45"  Sin  6  =  9.4951325        Cos  k  =9.660623'2 

~ 


e.  Remarks.  Look  out  tan  0,  cos  0,  and  sin  0,  at  one  search.  Use  either  check 
as  may  be  preferred.  This  operation  need  not  be  performed  oftener  than  the 
aemands  of  the  work  require,  the  plate  being  used  mean  time. 

13.  Remarks. 

The  observations  and  reductions  can  be  always  made,  according  to  the  process 
given,  without  a  watch,  but  the  latitude  of  the  place  must  be  known.  It  must  bo 
carried  on  a9  the  survey  proceeds,  by  measurement,  or  an  observation  made  to 
determine  it  with  the  instrument.  If  it  becomes  necessary  to  find  the  latitude  ill 
may  be  done  as  follows  : 

14.  Finding  the  Latitude  by  the  Sun. 

a.  Directions.     For  Observations.     Near  noon  begin  to  observe  the  sun 
a  little  before  it  reaches  its  greatest  altitude.      By  means  of  the  slow-motion 
screws  keep  the  sun's  image  exactly  in  place  on  the  screen,  or  by  direct  sight  keep 
the  cross-wires  exactly  on  the  sun.     As  it  moves  upward  just  carefully  follow  it, 
recollecting  that  the  object  is  to  get  its  greatest  altitude.      Be  careful  to  stop  fol- 
lowing it  when  it  turns  and  begins  to  descend. 

b.  Directions.     For  Reductions.    Find  z,  as  in  12,  b.    Find  the  sun's  appar- 
ent declination,  <5,  as  in  11,  c.     Then 

z  +  &  =  <£,  the  required  latitude  .....        (13) 
Be  sure  to  observe  the  Algebraic  signs,  as  6  may  be  -f  or  —  . 

c.  Remarks.     Having  the  latitude  in  this  way,  the  observations  and  reduc- 
tions may  be  conducted  according  to  the  processes  above  given.    The  latitude  once 
caref  ulty  ascertained  by  this  or  some  other  method,  may  be  preserved  by  the  dis- 
tance traversed  north  or  south  of  the  point  of  the  last  observation  for  latitude.    It 
will  at  once  appear  that  the  measurement  and  observation  may  be  made  to  check 
each  other.    The  method  of  reducing  the  change  in  latitude  by  linear  measurement 
may  be  as  follows: 

15.  Finding:  the  Latitude  by  Linear  Measurement. 

a.  Conditions.  The  latitude  of  the  point  measured  from,  or  reckoned  from, 
must  be  known.  The  measurements  must  be  reduced  to  the  north  and  south 
direction  from  the  reference  point.  Let  reduced  distances  north  be  -fv  and  those 
south  be  —  .  Let  all  signs  be  observed.  Let  the  true  bearings,  or  directions  of  all 
lines  with  the  meridian  of  the  reference  point,  be  given.  Let  any  number  of  courses 
be  run  in  any  direction. 


6.  Directions.  For  reducing  the  north  or  south  distances.  Multiply  the 
length  of  each  course  by  the  cosine  of  its  bearing,  the  results  being  given  signs 
as  above  indicated,  -f-  for  northerly  courses,  and  —  for  southerly  courses.  Sum 
these  results  regarding  the  signs. 

c.  Remarks.      This  sum  will  be  the  distance  north  or  south  of  the  reference 
point. 

d.  Directions.      For  reducing  feet  to  minutes  of  Latitude.     Find  the  length  of 
a  minute  of  latitude  for  the  place  by  this  equation. 

m  =  6076.36 


Then  divide  the  traversed  distance  north  or  south  of  the  reference  point  by  the 
value  of  m  found  from  this  equation. 

e.  Remarks.  The  result  will  be  the  minutes  and  decimals  of  a  minute  o^ 
the  new  point  from  the  reference  point.  This  value  of  m  will  be  in  feet,  hence  the 
north  or  south  distance  must  be  in  feet. 

16.  Remarks.  The  latitude  may  be  dispensed  with  during  a  day's  work 
after  the  first  satisfactory  observation.  It  may  be  for  a  longer  period  if  the  watch 
is  to  oe  depended  upon.  It  will  be  well  to  find  the  latitude,  and  check  the  work 
occasionally,  where  the  watch  is  used.  In  order  to  prepare  the  watch  for  this  work, 
proceed  as  follows : 

17.      Correcting  the  Watch. 

a.  Directions.     For  correcting  the  Watch  by  a  Noon  Observation.     Having 
ascertained  the  bearing  of  a  line  without  the  aid  of  the  watch,  as  at  first  directed, 
near  noon  set  the  line  of  sight  in  a  meridian.    Set  the  telescope  so  the  sun  can  be 
seen  in  it,  or  received  on  the  screen  as  it  passes  the  meridian.     Note  the  time  by 
the  watch  when  the  sun's  west  side  comes  in  apparent  contact  with  the  vertical 
cross-wire.    Note  the  watch  time  when  the  east  side  of  the  sun  just  touches  the 
vertical  wire.    Find  the  time  halfway  between  these  two  noted  times  for  the  time 
of  the  meridian  passage  of  the  sun's  center,  or  the  time  of  apparant  noon,  by  the 
watch. 

b.  Remarks.     The  time  as  above  found  should  differ  from  exact  noon  by 
just  the  equation  of  time  for  that  date  and  time  as  given  in  the  Nautical  Almanac. 
Observe  the  sign  there  attached  to  the  equation  of  time.    The  watch  may  then  be 
set  to  true  time  if  not  correct.    That  is,  it  may  be  set  so  that  the  time  of  the  sun's 
meridian  passage  will  be  just  the  equation  of  time,  with  its  sign,  from  exact  noon. 

c.  Remarks.    The  watch  may  also  be  corrected  directly  from  an  observation, 
reduced  as  at  first  directed  in  1C  and  12.    Here  it  will  be  necessary  to  take  the 
watch  time  of  the  observation,  as  directed  in  1C.    Having  done  so,  and  reduced  the 
observation  by  12,  proceed  as  follows : 

d.  Directions.     For  correcting  the  Watch  by  an  observation  at  any  time.    Hav- 
ing found  A  and  2,  and  knowing  <5,  find  t  by  the  following  equation. 

sin  A  sin  z 

Sm*=         C08d  <10> 

This  being  in  arc.  reduce  it  to  time  at  the  rate  of  four  minutes  of  time  to  one 
degree  of  arc. 

e.  Remarks.     This  result  should  differ  from  the  watch  time  of  the  observation 
from  mean  noon,  by  just  the  equation  of  time,  with  its  sign.    If  it  does  not,  set  the 
watch  so  it  would  have  done  so  had  the  observation  been  made  with  the  corrected 
watch. 

18.  Remarks.  Having  corrected  the  watch  by  the  last  method,  the  value  of 
t  in  time  may  be  found  from  the  value  of  t  at  this  observation  by  noting  the  time 
by  the  watch  of  another  observation,  and  thence  finding  the  elapsed  time.  This 
applied  to  the  first  value  of  t  will  give  its  value  for  the  last  observation.  Thus  the 
value  of  t  may  be  carried  forward  as  long  as  the  watch  runs  true.  Of  course  it  will 
occur  to  many  at  once  that  the  watch  can  just  as  well  be  used  to  measure  the 
elapsed  time  without  being  corrected.  This  is  too  careless.  The  better  way  is  to 
keep  a  careful  oversight  of  the  watch  by  correction.  Thereby  it  may  be  known 
how  much  the  watch  is  to  be  trusted.  It  is  always  best  to  establish  a  routine  sy» 
tern  in  these  matters,  as  soon  as  practicable,  and  adhere  faithfully  to  it. 


87 

19.  Remarks.  When  the  watch  is  corrected  by  either  method,  it  will  give 
-ne  value  of  t  in  time  directly  as  follows  :  Note  the  time  of  an  observation.  Apply 
to  this  time  the  equation  of  time  with  Us  sign,  as  given  in  the  Solar  Ephemeris  Table 
of  the  Nautical  Almanac.  The  result  will  give  the  apparent  time  of  the  observation 
from  apparent  noon,  -f-  when  the  sun  is  west  of  the  meridian,  and  —  when  it  is  east 
This  found  is  the  required  value  of  t. 

2O-    Reducing  Observations. 

«•    Conditions.     Let  the  notation  be  as  before. 

Let  t  =  the  sun's  apparent  hour  angle  at  the  time  of  the  observation,  that  is  the 
local  apparent  time  from  apparent  noon  This  is  -f-  when  W.  and —  when  E.  of  the 
meridian,  or  -f  for  P.M.,  and  —  for  A.M.  times. 

Let  the  value  of  (  be  found  by  18  or  19,  and  reduced  to  arc  at  the  rate  of  one 
degree  of  arc  to  each  four  minutes  of  time,  the  work  being  carried  out  to  seconds 
of  arc. 

o.  Directions.  For  finding  A  when  6.  «,  and  z  are  given.  Find  A  from  the 
following  equations. 


.^...  ~       sin   t 
Check-  c^  =  ^In-A 

c.    Example.     <J  =  18°  30' 20"  N.     z  =  52°  43' 30"    t  =  55°  46'  32"5 
Cos  6  =  9.9776554  ] 
Sin  t=  9.91 74225  h 

-£8950779  °|  Check. 

Sin  z  =  9.9007700  J    f 
Sin  A  =  9. 9943079     J 

20.  Remarks.    The  value  of  A  as  determined  in  these  examples  is  greater 
than  90°,  because  the  sun  is  south  of  the  zenith.     The  value  of  t  used  in  the  second 
example  was  found  from  the  first,  hence  the  exact  check.     It  may  be  noticed  how 
much  less  figuring  is  required  in  the  second  example  than  in  the  first.     It  should 
be  noted,  however,  that  more  than  one  check  is  figured  out  in  the  first  example, 
and  so  more  than  the  necessary  figures  shown.    The  value  of  A  is  carried  out  with 
exactness  in  order  that  the  process  may  be  fully  illustrated. 

21.  Summary.    Several  courses  are  hereby  opened  to  the  surveyor.     This 
is  done  that  he  may  have  the  more  checks  at  his  command,  and  so  make  certain  of 
his  work,     It  may  be  well  to  indicate  these  courses  in  a  catalogued  lorm  for  easy 
reference.    The  courses  are 

The  processes  of  ID,  12,  and  14  or  15. 

The  processes  of  1C,  12,  and  14  or  15,  and  thence 

16,  a,  or  16,  d,  and  18  or  19  and  2O. 

22.  Cautionary.     Keep  the  levels  and  the  vernier  of  the  vertical  circle  in 
good  adjustment.     Also  keep  the  adjustment  of  the  axes  of  the  instrument,  the 
transit  axis  and  the  vertical  axis,  in  good  order. 

23.  General  Remarks.    It  will  be  seen  that  in  doing  solar  work  with  these 
attachments  in  the  manner  explained  above,  the  observation  of  the  sun  depends  on 
the  ordinary  line  of  sight  of  the  telescope  exactly  as  in  all  Geodesic  work. 

For  this  reason  no  extra  adjustments  are  required.  The  accuracy  of  the  observa- 
tion in  no  way  depends  on  these  attachments,  which  are  merely  conveniences  to 
enable  one  to  make  solar  observations  with  the  ease  and  precision  of  ordinary 
terrestrial  work. 

Other  Solar  Attachments  are  mechanical  devices  requiring  special  adjustments, 
and  considerable  care  is  necessary  to  keep  these  adjustments  perfect,  while  they 
cause  some  degree  of  anxiety  and  doubt  in  the  mind  of  the  engineer  as  to  whether 
they  are  quite  perfect  or  not. 

With  this  invention  all  these  sources  of  anxiety  are  avoided,  the  solar  observation 
being  made  with  the  telescope  of  the  transit  itself,  while  it  has  the  advantage  of 
being  applicable  to  every  surveyors'  and  engineers'  transit,  is  so  light  as  not  to  add 
appreciably  to  the  weight  of  the  instrument,  so  simple  as  to  require  no  special  pro- 
vision for  its  care,  and  so  cheap  as  to  be  within  the  reach  of  every  surveyor. 


88 


On  Stadia  Measurement. 

Written  especially  for  this  Catalogue  by  GBO.  J.  SP*CHT,  C.  E.,  San  Francisco,  Cal. 

A  transit  or  theodolite,  which  is  provided  with  the  so-called  stadia  wires  and  a 
Tcrtical  circle,  furnishes  the  means  to  obtain  simultaneously  the  distance  and  the 
height  of  a  point  sighted  at  without  direct  measurement,  and  with  the  only  use  of 
a  self-reading  rod,  held  at  the  point  of  which  the  horizontal  and  vertical  position 
is  to  be  determined  in  reference  to  the  instrument-point. 

Besides  the  ordinary  horizontal  and  vertical  cross  hairs  of  the  diaphragm  of  the 
telescope,  two  extra  horizontal  hairs  are  placed  parallel  with  the  center  one,  and 
equally  distant  on  each  side  of  it,  which,  if  the  telescope  is  sighted  at  a  leveling 
rod.  will  inclose  a  part  of  this  rod  or  stadia-rod,  proportional  to  the  distance  from 
the  instrument  to  the  rod.  By  this  arrangement  we  have  obtained  an  angle  of 
sight,  which  remains  always  constant. 

Supposing  the  eye  to  be  in  the  point  O  (Fig.  1) , 
^       the  lines  O  e  and  O  k  represent  the  lines  of  sight 
Fig.lt  ^S\         from  the  eye  through  the  stadia-wires  to  the  rod, 

which  stands  consecutively  at  k  e,  i  d.  h  c,  g  b  and 
/  a.  According  to  a  simple  geometrical  theorem 
we  have  the  following  proportion  : 

Oa:Ob:Oc:Od:Oe=af:bg:ch:di:ek, 


which  means  that  the  reading  of  the  rod  placed 
on  the  different  points  a,  6,  c,  d  and  e  is  propor- 
«         *      «        tf      •  tional  to  the  distances  O  a,  O  6,  O  c,  O  d  and  O  e. 

The  system  of  lenses  which  constitute  the  telescope  do  not  allow  the  use  of  this 
proportion  directly  in  stadia  measurements,  because  distances  must  be  counted 
from  a  point  in  front  of  the  object  glass  at  a  distance  equal  to  the  focal  length  of 
that  lens. 


_f 
•  2 


Figure  2  shows  a  section  of  a  telescope  provided  with  stadia  wires. 
In  order  to  determine  the  distance  of  the  rod  from  the  instrument  it  will  be  neces- 
sary to  use  the  following  equations.     From  the  "law  of  lenses"  we  have  the  relation 

1  1  1. 


in  which  /,  and  /2  are  "conjugate  foci  "  and  /is  the  focal  length  of  the  object  glass. 
From  the  diagram  it  is  evident  that  0  C  :  A  B  =  0  D  :  ab.  If  we  let  p  =  the  dis- 
tance of  the  stadia  wires  from  each  other,  /,=  distance  0  C  and  a  =  the  space  on  the 
rod  AB,  and  D  the  distance  from  the  center  of  the  instrument  to  the  rod,  then  the 
second  equation  becomes  /2  :  a  =  /,  :  p.  Eliminating/!  from  these  equation  we  find  : 


or  we  may  write,  since  -=—  is  constant, 


=  a  k  4-  f : 


From  the  center  of  the  instrument  to  the  rod  the  distance  is 


c  being  the  distance  from  the  objective  to  the  center  of  the  instrument. 

Since  (c  -f/)  is  practically  a  constant  it  is  usually  denoted  by  the  single  letter  c 
and  is  known  as  the  "  constant  of  the  instrument." 


When  the  line  of  sight  is  not  level,  but  the  stadia  held  at  right  angle  to  it,  the 
formula  for  the  horizontal  distance  is : 
(2)  D  =  fc.a.cos  n  ~\-  c  -j-  om. 


The  member  om 


•--  sin  n ;  for  a  =  24',  n 


45°  the  value  of  om  is  but  8.4',  and  for 


o  =  10' ,  n  =  10°  it  is  0.86' ;  this  shows  that  om  in  most  cases  may  safely  be  omitted. 

Some  engineers  let  the  rodman  hold  the  staff  perpendicularly  to  the  line  of  sight ; 
they  accomplish  this  by  different  devices,  as,  a  telescope  or  a  pair  of  sights  attached 
at  right  angle  to  the  staff.  This  method  is  not  practicable,  as  it  is  very  difficult, 
especially  in  long  distances,  and  with  greater  vertical  angles  for  the  rodman  to  see 
the  exact  position  of  the  telescopes,  and  furthermore,  in  some  instances  it  is  entirely 
Impossible,  when,  for  instance,  the  point  to  be  ascertained  is  on  a  place  where  only 
the  staff  can  stand,  but  where  there  is  no  room  for  the  man.  The  only  correct  way 
to  hold  the  staff  is  vertically. 

In  this  case  we  have  the  following :  (Fig.  4) 

MF  =  c  +  GF  =  c  +  &.C.D. 
CD  must  be  expressed  by  AB. 
AB  =  a.    AGB  =  2m. 
CD  =  2GF  tan.m. 

And  finally,  after  many  transformations : 

D=c.cos  n-f-a.A;.cos2n  —  a.fc.sin2n  tanjrn. 

The  third  member  of  this  equation  may  safely  be  neglected,  as  it  is  very  small 
even  for  long  distances  and  large  angles  of  elevation  (for  1500',  n  =  45°  and  k=  100, 
it  is  but  0.02').    Therefore,  the  final  formula  for  distances,  with  a  stadia  kept  ver- 
tically, and  with  wires  equi-distant  from  the  center  wire,  is  the  following : 
(3)  D  =  C.POS  n-\-a.k.cos*n. 

The  value  of  c.cos  n  is  usually  neglected,  as  it  amounts  to  but  1  or  1.5  feet ;  it  is 
exact  enough  to  add  always  1.25'  to  the  distance  as  derived  from  the  formula 
(3a)  D  =  a.&.eos'n 

without  considering  the  different  values  of  the  angle  n. 

In  order  to  make  the  subtraction  of  the  readings  of  the  upper  and  lower  wire 
quickly,  place  one  of  the  latter  on  the  division  of  a  whole  foot  and  count  the  parts 


90 


included  between  this  and  the  other  wire ;  this  multiply  mentally  by  100  (the  con- 
stant &)  which  gives  the  direct  distance  D'. 

In  cases  where  it  is  not  possible  to  read  with  both  stadia  wires,  it  is  the  custom 
to  use  but  one  of  them  in  connection  with  the  center  wire,  and  then  to  double  the 
reading  thus  obtained.  "With  very  large  vertical  angles,  this  custom  is  not  advis- 
able, as  the  error  may  amount  to  0.50  % . 


Fig,4, 


j. 


To  find  the  height  of  the  point  where  the  stadia  stands  above  that  one  of  the 
Instrument,  simultaneously  with  the  distance,  we  have  the  following  : 

We  assume  in  reference  to  figure  4, 

9  =  height  of  instrument  point  above  datum. 

MP=  D  =  horizontal  distance  as  derived  from  formula  (3). 

n  =  vertical  angle. 

h  =  FE  =  stadia  reading  of  the  center  wire. 

Q  =  height  of  stadia  point  above  datum  ;  it  is 

Q  =  q  -f  D  tan  n  —  h. 

The  substraction  of  h  can  be  made  directly  by  the  instrument,  by  sighting  with 
the  center  wire  to  that  point  of  the  rod,  which  is  equal  to  the  height  of  the  telescope 
above  the  ground  (which  is  in  most  cases  =4.5")  ;  q  will  be  constant  for  one  and 
the  same  instrument  point  ;  then  the  formula  : 

Q  =  D  tan  n  ; 
this  in  connection  with  formula  (3)  gives 

Q  =  c  sin  n  -f-  «•&•  cos  n.  sin  n. 

or  Q  =  csinn      a. 


The  first  term  of  the  equation  can  be  neglected,  when  the  vertical  angle  is  not  too 
large  ;  hence  the  final  formula  for  the  height  is 

(5;  Q_a.fc.  8in2n 

2 

The  position  of  the  stadia  must  be  strictly  vertical. 

The  error  increases  with  the  height  of  m;  (m  =  height  of  center  wire  on  the 
rod).  In  shorter  distances  the  result  is  seven-fold  better  when  the  center  wire  is 
placed  as  low  as  one  foot  than  it  is  at  10'  ;  in  longer  distances  this  advantage  is 
only  double. 

It  is  always  better  to  place  the  center  wire  as  low  as  possible.  If  the  stadia  is 
provided  with  a  good  circular  level,  the  rodman  ought  to  be  able  to  hold  it  vertically 


91 

within  600";  that  means,  that  the  inclination  of  the  stadia  shall  not  be  more  than 
0.0-23'  in  a  10'  stadia,  or  0.034'  In  a  stadia  of  15'  length. 

Determination  of  the  two  constant  coefficients  c  and  k.  Although  the  stadia  wires 
are  usually  arranged  so  that  the  reading  of  one  foot  signifies  a  distance  of  ,100  feet, 
I  will  explain  here,  how  to  determine  the  value  of  it  for  any  case.  Suppose  the 
engineer  goes  to  work  without  knowing  his  constant,  and  not  having  adjustable 
stadia  wires.  The  operation  then  is  as  follows : 

Measure  off  on  a  level  ground  a  straight  line  of  about  1000'  length;  mark  every 
100',  place  the  instrument  above  the  starting  point,  and  let  the  rodman  place  his 
rod  on  each  of  the  points  measured  off;  note  the  reading  of  all  three  wires  separ- 
ately, repeat  this  operation  four  times ;  the  telescope  must  be  as  level  as  the  ground 
allows ;  measure  the  exact  height  of  the  instrument,  i.  e .,  the  height  of  the  telescope 
axis  above  the  ground.  Th^n  find  the  difference  between  upper  (o)  and  middle 
(m)  wire;  between  middle  (w)  and  lower  (M)  wire,  and  between  upper  (o)  and 
lower  (?*)  wire,  from  the  four  different  values  for  each  difference,  determine  the 
average  value;  then  solve  the  equation  for  the  horizontal  distance  (1)  D  =  fc.a-f-c., 
with  the  different  average  values,  and  you  find  the  value  of  k  and  c.  In  case  the 
stadia  wires  should  not  be  equi-distant  from  the  center  wire,  there  will  be  three 
different  constants,  one  for  the  use  of  the  upper  and  middle,  one  for  the  use  of  the 
middle  and  lower,  and  one  for  the  upper  and  lower  wire. 

If  the  stadia  wires  are  adjustable,  the  engineer  has  it  in  his  power  to  adjust  them 
so  that  the  constant  k  =  100,  or  k  =  200,  which  he  accomplishes  by  actual  trial  along 
a  carefully  measured  straight  and  level  line. 

The  constant  c,  which  is  usually  one  and  a  half  times  the  focal  length  of  the  object- 
glass,  can  be  found  closely  enough  for  this  purpose  by  focussing  the  telescope  for  a  sight 
of  average  distance,  and  then  measuring  from  the  outside  of  the  object-glass  to  the 
capstan-head  screws  of  the  cross-hairs.  This  constant  must  be  added  to  every  stadia 
sight;  it  may  be  neglected  for  longer  distances. 


Stadia  Measurements. 

Written  for  this  catalogue  and  manual  by  H.  C.  PEARSONS,  C.  E.,  Fenysburg,  Mich. 

In  view  of  the  great  and  growing  interest  in  the  subject  of  "  Stadia  Measurements,*' 
the  following  solution  of  the  problem  is  offered,  as  applied  to  inclined  measurements. 

This  solution  is  made  from  a  different  geometrical  consideration  than  that  usually 
employed,  and  it  effectually  does  away  with  the  necessity  for  any  subsequent  cor- 
rections, as  with  most  schemes  in  use  for  inclined  distances. 

In  the  following  discussion,  let 

R  =the  reading  of  the  stadia  rod; 

D  =  the  horizontal  distance  from  plumb  line  of  transit  to  stadia  rod,  which  must 

be  vertical. 

m  =  the  angle  of  elevation  or  depression  to  the  smaller  reading  of  the  stadia  rod. 
n  =  the  same  angle  to  the  larger  reading. 


Through  the  point  c,  at  the  distance  of  unity  from  the  centre  of  Instrument, 
dra^v  the  vertical  cb.  Then  the  rod  AB,  being  also  vertical,  the  triangles  a ob 
and  A  o  B  are  similar,  as  are  also  the  triangles  cob  and  C  o B.  But  the  read- 


92 

Jug,  R,  of  the  rod  AB  is  the  difference  of  the  tangents  of  the  angles  of  elevation, 
m  and  n.  Also,  the  distance  a  &  is  the  difference  of  the  tangents  of  these  angles, 
m  and  n,  to  distance  unity,  as  given  in  the  trigonometrical  tables. 

Whence,  to  find  the  horizontal  o  C  =  D,  we  have  simply  to  divide  the  reading  of 
the  "  Stadia  Hod"  by  the  difference  of  the  tangents  of  the  angles  of  elevation.  Or,  by 
formula, — 

p^  B 

Tan.  n  —  Tan.  m 

If  one  of  the  angles  should  be  a  depression  or  — ,  we  must  then  divide  by  the  aunt 
of  the  tangents,  and  the  formula  would  be 


D 


Tan.  n  -f-  Tan.  m 


Example.— It  n=  12°  16',  nat.  Tan  =  .217426 

"m=10°10',  "   "  =  .179328 

The  difference  of  the  tangents  =  .038098 

Then,  if  R  =  12.26  feet, 


It  may  happen  that  our  transit  has  no  vertical  circle,  or  that  we  have  no  trigono- 
metrical tables  at  hand.  In  either  case,  introduce  an  auxiliary  rod,  c  b  between  the 
stadia  rod  and  the  plumb-time  of  transit,  and  at  some  known  horizontal  distance,— 
preferably  100  feet,  —  from  the  latter,  and  note  the  intercept  a  6. 

This  intercept  is  the  analogue  of  the  difference  of  tangents  used  in  the  former 
case,  and  must  be  used  in  the  same  manner,  in  dividing  the  reading  of  the  stadia  rod, 
when  we  bhall  nave  the  distance,  D,  in  terms  of  the  distance  of  the  auxiliary  rod  from 
the  transit. 

Example.  —  Suppose  the  intercept  a  6  on  the  auxiliary  rod,  at  distance  100  feet,  13 
.845  foot,  and  that  the  reading  R,  of  the  stadia  rod  is  12  feet,  then 

oC  =  D  =  (12  -f-  .845)  X  100  =  1420  feet. 

If  the  height,  H,  of  the  foot  of  the  stadia  rod,  above  or  below  the  height  of 
Instrument,  be  wanted,  it  may  be  had  from  the  following  equation  : 

II  =  -|-  D  Tan.  m, 

in  which  the  +  sign  must  be  used  for  angles  of  elevation,  and  the  —  sign  for  those 
of  depression. 

Or  if  the  auxiliary  rod  be  used  instead  of  the  vertical  arc,  note  the  intercept  a  b 
on  this  rod,  between  the  level  line  oC  and  the  line  of  sight  to  the  foot  of  the  stadia 
rod,  and 

Multiply  this  intercept  by  the  ratio  ofDto  oc. 

Example—  in  the  last  case,  If  ca  =  1.06  ft,  oc  being  100  feet,  and  D  =  1420  ft. 
then 


CA  =  H  =  ca  -       «•  1.06          =  16.05  feet. 


The  Adjustments  of  the  Auxiliary  Telescopes  of  Mining 

Transits. 

The  Detachable  Side-Telescope. 

This  telescope,  illustrated  on  page  189,  as  ordinarily  made,  is  attached  to  the 
transverse  axis  of  the  mam  telescope  by  means  of  a  hub,  which  is  screwed  upon  a  pro- 
longation  of  this  axis  beyond  the  .standards.  The  hub  contains  an  independent  hori- 
zontal axis  upon  which  the  side-telescope  may  be  revolved,  and  to  which  it  may  be 
clamped.  The  side-telescope  is  usually  set  parallel  to  the  main  telescope,  and  look- 
ing in  the  same  direction,  but  it  may  be  set  so  that  it  is  inclined  at  a  given  verti<  al 
angle  when  the  main  telescope  is  horizontal.  A  counterpoise  is  attached  to  the  other 
end  of  the  transverse  axis  of  the  main  telescope,  so  as  to  balance  the  weight  of  the 
side-telescope  and  retain  that  axis  horizontal  when  the  side-telescope  is  in  use.  The 
side-telescope  is  mainly  intended  as  an  auxiliary  in  measuring  vertical  angles,  and  it 
is  on  this  account  that  the  simple  means  of  attaching  it  to  the  transit,  here  described, 
has  been  adopted  by  us  as  sufficient  for  the  purpose,  although  it  will  be  very  diffi- 
cult to  place  its  line  of  collimation  truly  parallel  to  the  main  telescope  for  all  focus- 
sing positions  of  the  object-slide. 

The  adjustments  of  the  detachable  side-telescope  are  as  follows :  — 

1.  To  place  its  vertical  wire  perpendicular  to  the  transverse  axis  of  the  instru- 
ment.    Attach  the  side-telescope  and  the  counterpoise  to  the  transverse  axis. 
Clamp  the  side-telescope  slightly  to  its  hub,  bisect  a  point  by  its  vertical  wire  and 
move  the  main  telescope  on  its  horizontal  axis  of  revolution.    If  the  point  remains 
bisected  by  the  vertical  wire  of  the  side-telescope  throughout  its  entire  length  this 
adjustment  is  correct.    If  not,  loosen  the  capstan-headed  screws  and  rotate  the 
reticule  bearing  the  wires,  as  explained  on  page  58,  until  the  wire  bisects  the  point 
throughout  its  entire  length.    Then  slightly  tighten  the  capstan-headed  screws  as 
explained  in  "Some  Remarks  Concerning  Instrument  Adjustments,"  page  20.    Also 
see  page  58. 

2.  To  place  the  intersection  of  the  cross-wires  of  the  side-telescope  in  its  line 
of  collimation.    This  may  be  done  in  several  ways. 

(a)  The  side-telescope  being  detachable,  it  could  be  adjusted  by  rotating  it  in 
wyes,  were  any  at  hand.    Such  wyes,  as  we  have  shown  before,  may  be  impro- 
vised by  cutting  the  proper  shapes  out  of  thin  wood,  and  fastening  a  pair  of  them 
to  a  board  in  au  upright  position.    The  distance  between  them  should  be  such  that 
the  telescope  may  rest  upon  the  outside  of  the  mounting  of  the  object-glass  and 
against  its  shoulder  where  the  cap  is  placed,  and  upon  the  tube  near  the  cross- 
wires  when  practicable.     The  improvised  wyes  being  placed  on  a  firm  support 
and  fastened  so  that  they  will  not  move,  the  side-telescope  may  be  revolved  in 
them,  and  the  wires  may  be  placed  in  the  line  of  collimation  as  in  a  wye-level,  using 
a  distant  point.    The  horizontal  wire,  being  the  more  important  one  in  the  side- 
telescope,  should  be  placed  with  some  care. 

(b)  This  adjustment  for  colliraation  may  be  made  without  removing  the  side- 
telescope,  if  for  the  adjustment  of  the  horizontal  wire,  a  small  spirit-level*  mounted 
on  a  metal  base,  similar  to  those  described  on  page  119,  is  at  hand.    Then  proceed 
thus: 

Adjustment  of  the  horizontal  wire,  First,  level  up  the  instrument  by  its  plate 
levels.  Then,  placing  the  main  telescope  in  a  horizontal  position  by  its  levels 
find  a  well-defined  object,  such  as  the  target  of  a  leveling  rod,  distant  about  300  feet 
Now  clamp  the  side-telescope  when  in  a  nearly  horizontal  position  to  its  hub,  and 
placing  the  auxiliary  level,  which  has  been  previously  adjusted,  longitudinally  on 
the  side-telescope  bring  its  bubble  to  the  center  of  the  tube  by  means  of  the  tan- 

*  Such  a  spirit-level  mounted  in  a  cast-iron  frame,  and  good  enough  for  this  purpose  if  carefully  selected, 
tut  be  bought  in  any  of  the  better  equipped  hardware  stores. 


94 

gent  screw  of  the  main  telescope  and  now,  by  turning  the  instrument  on  its  vertical 
center  see  if  the  horizontal  wire  of  the  side-telescope  bisects  the  object  or  target 
also.  If  so,  this  adjustment  is  made,  but  if  not,  it  must  be  completed  by  moving  the 
vertical  capstan-headed  screws  as  explained  on  page  58. 

To  verity  this  adjustment,  the  side-telescope  may  be  reversed  on  its  horizontal 
axis  of  revolution  and  clamped  to  its  hub  when  nearly  in  the  same  level  plane. 
Then  turn  the  instrument  a  little  more  than  180°  on  its  vertical  center,  place  the 
auxiliary  level  on  the  side-telescope,  same  as  before,  and  bring  the  bubble  to  the 
center  of  its  tube  by  means  of  the  vertical  tangent  screw.  If  now,  when  the  side- 
telescope  is  in  the  reversed  position  the  horizontal  wire  bisects  the  object  also,  this 
adjustment  is  completed,  but  if  it  does  not  then  the  horizontal  wire  must  be  moved 
again  to  a  point  half-way  between  the  two  readings. 

This  adjustment  may  also  be  made  by  the  auxiliary  level  alone  or  by  means  of 
a  striding-level  without  the  aid  of  the  main  telescope  (see  page  140). 

Adjustment  of  the  vertical  wire.  Select  a  well  defined  object,  as  a  church  spire, 
distant  5  or  6  miles.  Bisect  it  with  the  vertical  wire  of  the  main  telescope,  and 
without  moving  the  instrument,  look  through  the  side-telescope  and  note  whether 
the  object  is  also  bisected  by  its  vertical  wire.  If  not,  make  the  adjustment  by 
moving  its  vertical  wire  by  the  horizontal  capstan-headed  screws,  until  the  object 
is  bisected  also.  The  distance  between  the  two  telescopes  being  only  a  few 
inches,  the  vertical  wires  will  cover  so  great  a  width,  if  the  object  be  sufficiently 
distant,  that  the  effect  of  the  excentricity  of  the  side-telescope  will  be  almost  im- 
perceptible and  the  same  distant  point  may  be  used  for  each  telescope. 

(c)  When  a  distant  object  is  not  available,  measure  with  a  pair  of  dividers  the  ex- 
centricity of  the  side-telescope,  which  is  the  distance  between  the  centers  of  the  two 
telescopes.  Then  transfer  it  to  the  face  of  a  wall  as  far  distant  as  practicable  and 
make  two  marks  whose  horizontal  distance  apart  is  equal  to  this  excentricity.  Bisect 
one  of  these  marks  by  the  vertical  wire  of  the  main  telescope  and  then  look  through 
the  side-telescope  and  note  whether  the  other  mark  is  bisected  by  its  vertical  wire.  If 
not,  make  it  do  so  by  moving  the  cross-wires  of  the  side-telescope  as  described  on  page 
58.  The  direction  of  the  lines  of  sight  should  be  at  right  angles  to  the  surface  upon 
which  the  two  marks  are  made. 

The  position  of  the  side-telescope  with  respect  to  the  main  telescope  should  be 
assured  whenever  the  former  is  to  be  used.  This  may  be  done  as  follows  :  find  a  mark 
that  is  bisected  by  the  horizontal  wire  of  the  main  telescope.  Then  turn  the  instru- 
ment on  its  vertical  axis  and  notice  whether  the  horizontal  wire  of  the  side-telescope 
bisects  the  same  mark.  If  so,  firmly  clamp  the  side-telescope  to  its  hub.  If  not, 
gently  tap  one  end  of  the  side-telescope,  which  hitherto  has  only  been  loosely  clamped, 
until  its  horizontal  wire  coincides  with  the  mark  and  then  clamp  the  side-telescope  to 
its  hub.  The  telescopes  are  now  set  to  correspond  with  the  zero  of  the  vertical  circle. 

To  place  the  telescopes  at  an  angle  with  each  other.  Level  up  and  fix  a  mark 
when  the  main  telescope  is  level.  Then  raise  or  depress  the  main  telescope  the  required 
angle  and  clamp  the  horizontal  axis.  Now  move  the  side-telescope  until  its  horizontal 
wire  bisects  the  mark  and  clamp  it  firmly  to  its  hub.  During  an  extended  operation  with 
the  side-telescope,  the  relative  position  of  the  two  telescopes  should  be  verified  from 
time  to  time  to  detect  any  disturbance  of  the  side-telescope. 

Transits  having  the  telescope  mounted  at  the  end  of  the  horizontal  axis  of  revolu- 
tion are  sometimes  used  in  mines ;  or,  as  shown  in  the  Alt-Azimuths  Nos.  If  a  and  16b, 
this  construction  is  used  in  some  instruments  for  geodetic  and  smaller  astronomical 
work.  The  adjustment  of  such  a  telescope  for  cpllimation  may  therefore  be  explained 
in  this  connection.  The  following  method  is  as  simple  as  any :  — 

Select  a  well-defined  object,  as  a  church-spire,  distant  at  least  5  or  6  miles.  The 
^istrument  being  leveled,  bisect  the  object  with  the  vertical  wire  and  read  the  verniers 
of  the  horizontal  limb.  Then  turn  the  vernier  plate  so  as  to  read  exactly  18u°  different 
from  the  previous  reading,  and  revolve  the  telescope.  If  the  vertical  wire  is  adjusted 
for  collimation  it  will  again  bisect  the  distant  object,  since  the  space  covered  by  the 
cross- wires  on  an  object  at  such  a  distance  will  be  much  greater  than  the  change  in  the 
position  of  the  telescope  as  caused  by  its  excentricity  from  the  center  of  the  instrument. 
If  it  does  not  again  bisect  the  object,  correct  one-half  the  error  by  means  of  the  hori 
zontal  capstan-headed  screws  as  explained  on  page  58. 


95 

The  adjustment  of  the  horizontal  wire  for  coilimation  may  be  made  by  selecting 
one  of  the  methods  best  adapted  for  a  particular  design  of  telescope. 

These  two  adjustments  should  be  repeated  until  both  are  correct. 

To  measure  the  excentricity  of  the  telescope,  set  up  the  instrument  as  near  to 
a  wall  or  other  vertical  object  as  possible.  Draw  a  horizontal  line  upon  the  wall 
at  a  convenient  height.  Point  the  telescope  exactly  at  right  angles  to  the  wall, 
mark  where  the  vertical  wire  intersects  the  line  just  drawn,  and  read  the  verniers 
of  the  horizontal  limb.  Turn  the  vernier  plate  exactly  180°,  revolve  the  telescope 
and  make  a  second  mark  where  the  vertical  wire  now  intersects  the  line.  The  dis- 
tance between  these  two  marks  will  be  twice  the  excentricity  of  the  telescope. 

When  using  an  instrument  of  this  description  for  short  sights,  it  is  very  con- 
venient to  use  sighting  poles  with  excentric  targets,  or  an  offset  at  the  foot  of  the 
pole  corresponding  to  the  excentricity  of  the  telescope. 

The  Auxiliary  Top  Telescope, 

Now  superseded  by  the  interchangeable  auxiliary  telescope,  see  style  I. 

This  auxiliary,  as  previously  made  by  us,  was  mounted  in  adjustable  wyes  on 
standards  permanently  fixed  to  the  main  telescope,  so  that  both  lines  of  sight  could 
be  made  parallel.  The  weight  of  the  top  telescope  was  balanced  by  a  counterpoise 
attached  to  a  stem  also  permanently  fixed  to  the  cross-axis  of  the  main  telescope. 
When  the  top  telescope  was  not  in  use  it  was  kept  in  the  instrument  box,  while  the 
standards  and  counterpoise  stem  were  permanently  fixed  to  the  main  telescope  so  as 
to  avoid  frequent  and  tedious  adjustments.  This  feature  made  the  instrument 
troublesome  and  unwieldy  for  the  more  ordinary  work  in  mines,  and  still  less  con- 
venient for  surface  work. 

This  improvement  when  first  introduced  by  us  superseded  all  other  forms  of  top 
telescopes  as  made  by  others  whose  main  object  seemed  to  be  simply  to  straddle  an- 
other telescope  above  the  main  one  (a  mere  commercial  article,  not  an  instrument 
of  precision)  for  the  purpose  of  steep  sighting.  But  since  the  line  of  sight  of  such  a 
telescope  can  never  be  placed  truly  at  right  angles  to  the  cross-axis,  the  line  of  coili- 
mation does  not  move  in  a  truly  vertical  plane,  therefore  horizontal  angles  measured 
between  points  differing  greatly  in  elevation  or  in  distance  are  never  correct. 

It  can  also  be  readily  seen  that  the  telescope  of  a  solar  attachment  as  commonly 
made,  having  no  means  of  lateral  adjustment  to  the  main  telescope,  is  insufficient  in 
this  respect  (even  leaving  aside  its  low  power  and  aperture)  and  cannot  meet  tlie 
requirements  properly.  The  adjustment  by  which  the  line  of  coilimation  of  top 
telescope  is  placed  in  the  same  vertical  plane  as  that  of  the  main  telescope  is  just  as 
important  as  that  of  the  main  telescope  itself. 

A  most  convenient  and  practical  device  haying  all  the  advantages  of  that  former 
style,  i.  e.,  means  of  adjusting  the  line  of  coilimation  parallel  to  that  of  the  main 
telescope,  so  that  after  having  been  removed  it  will  retain  its  adjustments  when  again 
attached,  is  our  new  mounting  of  the  top  telescope  by  means  of  threaded  studs.  This 
enables  the  engineer  to  read  horizontal  angles  when  the  main  telescope  cannot  be 
used,  obviating  the  making  of  corrections  for  the  eccentricity  of  the  telescope. 

Patent  Adjustable  Top  Telescope. 

This  device  consists  of  an  adjustable  auxiliary  telescope  (see  pages  189  and 
193)  and  an  open  central  pillar,  which  latter  screws  to  a  threaded  stud  cast  on  or 
permanently  secured  to  the  cross-axis  of  the  main  telescope.  When  not  needed, 
the  auxiliary  telescope  and  its  counterpoise  may  be  returned  to  the  box  and  the 
instrument  is  free  of  incumbrances,  save  the  stem  for  the  counterpoise  and  the 
stud  to  which  the  central  pillar  carrying  the  auxiliary  telescope  is  attached,  and  is 
ready  for  surface  work. .  If  desired,  the  top  telescope  may  be  entirely  unscrewed 
from  the  central  pillar,  leaving  the  latter  attached  to  the  main  telescope. 

The  Adjustment  of  the  Auxiliary  Telescope  used  as  a  Top  Telescope:  — 
It  is  assumed  that  all  adjustments  of  the  transit  proper  have  been  made,  that  is, 
that  the  plate  and  telescope  levels,  the  line  of  coilimation,  the  vertical  plane,  etc., 
have  been  verified  and  corrected,  and  that  the  verniers  of  the  vertical  circle  read 


96 

zero  when  plates  are  leveled  up  and  that  the  bubble  of  the  telescope  level  is  in  the 
center  of  its  graduation. 

The,  adjustment  of  Line  of  Collimation  of  Auxiliary  Telescope  :  First  examine  the. 
coincidence  of  the  intersection  of  the  cross  wires  with  the  optical  axis.  This  may 
be  done  by  rotating  the  telescope  in  improvised  wyes  of  wood  (see  p.  93),  or  by 
rotating  it  in  the  socket  of  the  pillar  [as  sometimes  made  by  us]  by  unscrewing  it 
about  one  turn,  when  the  adjustment  is  made  by  moving  the  capstan-headed  screws 
as  described  on  page  58.  The  telescope  must  now  be  screwed  to  its  bearing  in  such 
a  manner  that  the  cross-wires  are  parallel  to  those  of  the  main  telescope — to  be  veri- 
fied as  explained  in  "To  make  the  vertical  wire  perpendicular  to  the  plane  of  the 
horizontal  axis,"  etc.,  p.  54. 

To  place  the  line  of  collimation  of  the  auxiliary  telescope  in  the  same  vertical  plant 
with  that  of  the  main  telescope.  Bisect  a  distant  object  with  the  vertical  wire  of  the 
main  telescope  ;  see  if  the  venical  wire  of  the  auxiliary  telescope  also  bisects  the  same 
point.  If  not,  move  the  auxiliary  telescope  by  means  of  the  pair  of  opposing  milled- 
headed  screws  attached  to  its  pillar  nearer  the  eye-end  until  the  distant  object  is 
bisected  at  the  same  time  by  both  vertical  wires.  Now  focus  the  main  telescope  on  a 
near  object  and  see  if  the  vertical  wire  of  the  auxiliary  telescope  bisects  the  same 
point  as  the  vertical  wire  of  the  main  telescope.  If  not,  make  the  adjustment  by 
means  of  the  pair  of  capstan-headed  opposing  screws  on  one  side  of  the  adjusting 
trivets  of  the  pillar.  Then  re-examine  both  wires  for  coincidence  with  the  distant 
object,  u-ing  the  milled-headed  screws,  and  also  repeat  the  adjustment  for  near  object 
if  necessary.  The  two  lines  of  collimation  are  now  in  the  same  vertical  plane. 

To  adjust  the  top  telescope  so  that  both  horizontal  wires  bisect  the  same  distant 
object.  Bisect  a  distant  object  with  the  horizontal  wire  of  the  main  telescope,  and  see 
whether  the  horizontal  wire  of  the  auxiliary  telescope  bisects  the  same  point.  If  not, 
make  the  coincidence  by  means  of  the  pair  of  opposing  capstan  screws  in  the  trivets 
near  the  milled-headed  screws.  This  being  done,  both  these  adjustments  should  be 
verified  and  repeated  if  necessary.  These  adjustments  once  carefully  made  assure 
the  exact  parallelism  of  both  telescopes  and  will  not  require  repetition  except  at  long 
intervals,  or  after  an  injury. 

The  distance  between  the  lines  of  sight  of  the  two  telescopes  should  be  carefully 
measured  by  sighting  at  a  vertical  line  on  a  wall  —  the  telescopes  being  horizontal  — 
when  the  distance  between  the  intersections  of  the  two  horizontal  wires  on  the  line  will 
be  the  eccentricity  of  the  top  telescope,  for  which  every  vertical  angle  measured  with 
it  should  be  corrected. 

The  Berger  Style  I  Interchangeable  Auxiliary 
Telescope  (Patented). 

See  pages  189  and  193. 

In  this  device  Style  I,  the  auxiliary  telescope  screws  direct  upon  an  open  central 
vertical  post  cast  in  one  piece  with  the  transverse  axis  to  secure  great  rigidity,  the 
degree  of  accuracy  of  the  result  depending  in  a  large  measure  upon  the  degree  of 
accuracy  with  which  the  center  of  the  pillar,  and  the  line  of  collimation  of  the  prin- 
cipal (then  vertical)  wire  of  the  auxiliary  telescope  are  made  to  lie  in  the  same  verti- 
cal plane  as  the  optical  axis  of  the  main  telescope  or  parallel  to  it.  With  the  care 
given  to  it  and  special  machinery  used  for  it,  this  condition,  difficultas  it  is,  is  secured 
to  an  extent  which  leaves  little  to  be  desired  for  all  practical  purposes.  As  the  aux- 
iliary telescope  is  inter  changeable  from  top  to  side  there  is  really  need  of  but  one  wire, 
which  we  will  designate  as  the  principal  wire.  This,  when  the  auxiliary  is  mounted 
on  top,  is  the  vertical  wire,  and  when  on  the  side  becomes  the  horizontal  wire.  There- 
fore it  will  be  seen  that  when  the  auxiliary  is  mounted  on  top  the  line  of  collimation 
of  its  horizontal  wire  is  immaterial,  as  no  vertical  angles  will  then  be  measured. 
When  the  latter  are  to  be  measured  the  engineer  will  then  mount  the  auxiliary  on 
the  side,  when  in  turn  the  vertical  wire  becomes  immaterial.  The  auxiliary  tele- 
scope is  provided  with  two  milled-headed  opposing  screws  for  ranging  in  line  with  the 
main  telescope.  The  auxiliary  telescope's  adjustment  of  collimation  and  coincidence 
of  the  cross-wires  and  optical  axis  must  be  verified  by  the  use  of  improvised  wooden 
wyes  (see  above),  should  it  become  necessary. 

The  success  which  the  interchangeable  auxiliary  telescope  has  achieved,  both 
here  and  abroad,  since" first  invented  by  this  firm  in  1895  is  somewhat  phenomenal. 
It  shows  that  this  combination  is  the  most  applicable  one  in  solving  the  difficult 
problems  arising  in  mine  engineering.  For  this  reason  every  preparation  has  been 
made  to  meet  the  demand  and  new  improvements  are  added  as  experience  may  sug- 
gest. All  our  top  telescopes  are  therefore  now  made  interchangeable. 


97 

The  Use  of  the  Interchangeable  Auxiliary  Telescope 
for  Astronomical  Observations. 

Besides  its  ordinary  use  for  steep  sighting  in  mines,  the  interchangeable  auxiliary 
telescope,  as  described  in  the  foregoing  article,  will  at  times  be  found  very  useful  as 
an  astronomical  instrument.  It  is  particularly  advisable  in  making  latitude  observa- 
tions by  meridian  altitude  and  in  observing  transits  across  the  meridian  for  time.  As 
a  rule  when  the  prism  is  attached  to  the  eye-piece  of  the  main  telescope  it  is  not  pos- 
sible with  the  engineer's  mining  transit  to  point  the  telescope  at  a  greater  angle  of 
elevation  than  about  70°,  consequently  it  would  be  impossible  to  make  solar  observa- 
tions at  a  latitude  lower  than  40°  when  the  sun  is  at  its  greatest  declination  or  obser- 
vation on  Stars  near  the  zenith.  However,  by  attaching  the  prism  to  the  auxiliary  telescope 
used  asatop  or  sidetelescope,  these  observations  may  be  made  witheasenndthisdifficulty  overcome 

In  making  latitude  observations  the  interchangeable  auxiliary  telescope  should  be 
attached  at  the  side ;  and  its  horizontal  wire  is  then,  by  means  of  the  two  oppos- 
ing tangent  screws,  made  to  correspond  to  the  line  of  collimation  of  that  of  the  main 
telescope  by  bisecting  with  both  telescopes  some  distant  and  well-defined  object :  then, 
if  a  meridian  mark  is  used  (which  is  not  absolutely  necessary),  the  transit  should  be 
set  up  in  the  meridian  by  the  main  telescope  and  the  pointing  on  the  sun  or  star  may  be 
made  with  the  auxiliary  telescope  with  or  without  the  prism,  as  conditions  may  require. 

In  observing  transits  the  auxiliary  telescope  should  be  mounted  on  top  and  ranged 
into  line  with  the  vertical  wire  of  the  main  telescope  by  using  the  two  opposing 
screws  as  explained. 

In  making  solar  and  stellar  observations  with  the  main  telescope  and  prism  attachment,  the  tele- 
acope  should  always  be  reversed  through  the  standards  with  the  objective  down  instead  of  up 


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99 

Magnetic  Needle  of  Edge-bar  Form 

The  needle  shown  in  the  cross  section  of  our  Transit  compass  also  in  the  top  view 
on  opposite  page,  represents  the  form  adopted  and  preferred  by  us  for  all  of  our  com- 
pass instruments,  because  it  has  its  greatest  dimensions  in  the  vertical  direction  ;  hence 
its  name.  At  the  ends,  where  it  is  read,  it  is  quite  thin,  but  increases  in  thickness 
symmetrically  towards  the  central  part  to  give  it  the  rigidity  necessary  to  retain  the  true 
longitudinal  shape  and  yet  be  very  light  of  weight  to  minimize  the  dulling  of  the  pivot 
on  which  it  swings.  The  point  of  suspension  in  the  steel  cap*  and  the  two  ends  of  the 
needle  are  in  a  straight  line,  thereby  forming  the  geometric  axis. 

The  advantage  derived  from  the  edge-bar  form,  therefore,  is  that  its  mag- 
netic axis  must  be  contained  in  the  geometric  axis  of  the  needle,  whence  it 
follows  that  there  is  no  index  error  at  its  reading  ends. 

This  cannot  be  claimed  for  a  needle  of  the  flat,  oblong  type,  since  its  magnetic 
axis  may  follow  the  grain  imparted  to  it  in  rolling  the  steel  ingot.  In  such  a  needle 
the  index  error  may  be  negligible  or  amount  to  a  great  deal,  according  to  size  and 
shape.  Hollow,  cylindrical,  and  elliptically  shaped  needles  are  not  exempt  from  this 
error,  and  as  their  ends  require  brass  extensions  for  reading  the  graduation  in  a  sur- 
veyor's compass,  the  effective  length  of  the  needle  is  not  only  shortened,  but  the  exten- 
sions in  themselves  may  become  an  additional  source  of  index  error.  As  will  be  seen 
in  the  cross  section,  the  center  of  gravity  in  the  edge-bar  form  is  very  much  below  the 
point  of  suspension,  which,  together  with  the  increasing  weight  of  the  needle  toward 
its  central  part,  makes  it  less  sensitive  to  dip.  The  quivering  of  a  needle  so  constructed 
is  not  annoying,  since  the  center  of  its  quivering  motion  is  in  line  through  its  two  ex- 
treme points,  which  are,  therefore,  stationary.  Permanent  magnet  steel  is  used  only 
in  its  construction,  which,  when  properly  hardened,  will,  at  all  times,  retain  sufficient 
magnetism  to  give  the  needle  direction  when  resting  on  a  sharp  point.  It  is  the  dulling 
of  the  latter  t  which  is  commonly  at  fault  when  a  needle  does  not  settle  repeatedly  in 
the  same  place  —  not  loss  of  magnetism  as  is  generally  supposed  —  and  most  of  this 
difficulty  may  be  obviated  by  carefully  raising  or  lowering  the  needle  and  not  allowing 
the  needle  to  play  when  shouldering  the  instrument.  To  be  light  the  steel  cap  is  mounted 
in  an  aluminum  cell. 


*  It  is  our  belief  that  no  advantage  whatever  is  gained  by  suspending  the  needle  on  jewel 
bearings,  but  that  a  properly  tempered  steel  bearing,  resting  on  a  steel  pivot  of  a  different  temper, 
is  superior  to  the  jewel  mounting.  We  find  that  in  the  instruments  sent  us  for  repair  the  jewels 
are  almost  always  grooved  by  the  wear  of  the  pivot  so  that  it  is  difficult,  or  impossible,  to  repair 
them  satisfactorily.  With  steel  bearings  no  such  difficulty  is  encountered.  As  to  danger  of  rust- 
ing, it  is  certainly  no  greater  for  the  bearing  than  for  the  pivot,  and  the  instruments  sent  in  for 
repair  do  not  often  show  signs  of  either  bearing  or  pivot  rusting. 

t  In  order  to  partially  remedy  the  wearing  on  the  point  we  sometimes,  upon  special  request,  furnish  a 
needle  of  twisted  form  which  can  be  made  very  Tight  and  be  quite  stiff  in  proportion  to  its  weight.  It  is  not 
of  a  strictly  -scientific  shape  but  answers  the  requirements  of  a  Surveyor's  Compass. ,;  The  needle  consists  of  a 
flat  bar  of  ye5™  thin  permanent  magnet  steel.  At  the  central  portion  of;  the  ,bar,  the  blade  is  horizontal, 
while  at  the  ends  it  is  vertical  as  in  the  edge-bar  form  of  needle.  Between  the  center  and  the  ends  there  are 
several  twists  in  the  bar.  The  points  of  the  needle  and  the  point  of  suspension  are  all  in  the  same  straight 
line  in  this  new  needle,  as  in  the  old.  The  center  of  gravity  is  placed  as  far  below  the  point  of  suspension  as 
the  necessarily  limited  depth  of  the  Transit  compass  permits,  but  owing  to  its  extreme  lightness  the  center  of 
gravity  should  be  carried  much  farther  bilow  than  the  old  to  counteract  the  dip  to  the  same  extent.  In  conse- 
quence tlie  needle  of  twisted  form  is  more  easily  affected  by  change  in  latitude  and  its 
application  is,  therefore,  limited,  to  use  within  latitudes  differing  not  more  than  a  few  degrees. 

Caution. 

The  magnetic  needle  must  always  be  lowered  very  gently  on  its  pivot.  The 
knob  marked  "Lifter"  (see  page  98)  raises  and  lowers  the  needle.  If  the  needle  is 
lowered  abruptly  upon  the  pivot,  its  fine  point  may  be  dulled  the  first  time,  and  the 
needle  will  then  work  sluggishly  and  not  settle  twice  in  the  same  place. 

To  use  the  Variation  Plate,  insert  an  adjusting  pin  into  the  capstan-headed  nut 
beneath  the  "Lifter,"  and  by  turning  either  way  the  desired  declination  may  be  set 
for  East  or  West. 


100 


Berger  Short  Focus  Lenses. 


A  sectional  view  of  a  Berger  Short  Focus  L»ens  attached  to 
an  Erecting"  Transit  Telescope. 


No.  1  and  2  Lenses. 


No.  1  Lens. 


The  above  lenses  may  be  attached  separately  or  together,  as 
shown;  for  a  complete  description  see  opposite  page. 


101 


The  Berger  Short  Focus  Lens  Attachment. 

A  very  valuable  addition  to  the  engineer's  outfit  is  found  in  the  short  focus  lens 
attachment  which  has  been  brought  out.  The  contrivance  is  simple,  but,  like  many 
simple  devices,  is  very  effective  in  overcoming  a  practical  difficulty.  Probably  every 
engineer  has  been  annoyed  by  being  obliged  to  sight  a  point  a  little  too  near  for  the 
telescope  to  focus.  Most  transit  telescopes  will  not  focus  on  a  point  much  nearer  than 
6  or  6  feet  (levels  not  nearer  than  7  or  8  feet)  away  from  the  instrument,  while  it  is 
frequently  necessary  to  sight  a  point  on  the  ground  nearly  under  the  transit,  at  a  dis- 
tance which  is  usually  less  than  that. 

In  mine  surveying  as  well  as  inside  of  factory  buildings,  one  frequently  needs  to 
sight  a  point  overhead  or  on  the  walls  and  very  near  the  transit.  Ordinarily  the  only 
way  out  of  the  difficulty  is  to  focus  as  nearly  as  possible  and  do  the  rest  by  a  guess. 
As  a  further  instance,  one  often  finds  in  leveling,  that  it  will  be  necessary  to  take 
a  reading  on  a  point  very  near  the  instrument,  and  has  to  resort  to  various  means 
(all  of  them  inaccurate)  of  getting  around  the  difficulty.  The  attachment  men- 
tioned consists  of  a  small  aluminum  tube  containing  a  simple  lens,  which  is  attached  in 
front  of  the  objective.  The  lens  is  so  placed  in  the  tube  that  it  can  be  accurately 
centered  by  means  of  4  adjusting  screws.  The  effect  of  this  lens  is  of  course  to  bring 
rays  to  a  focus  nearer  to  the  objective,  and  thus  enable  the  observer  to  focus  a  nearer 
object  than  would  otherwise  be  possible.  When  the  telescope  will  focus  no  nearer  than 
6  feet,  the  attached  lens,  marked  1,  is  ground  so  that  it  will  focus  objects  6  feet  away 
when  the  objective  tube  is  drawn  away  in.  This  allows  the  entire  motion  of  the  focusing 
slide  for  distances  between  6  and  4  feet.  For  distances  nearer  than  4  feet  a  second 
lens  may  take  the  place  of  the  first  and  will  focus  up  to  about  2|  feet.  If  the  two  are 
used  at  once  the  distance  is  reduced  to  about  two  feet. 

With  this  pair  of  lenses  there  is  no  distance  between  two  feet  and  infinity  at  which 
objects  cannot  be  focused.  The  accuracy  of  work  done  with  this  attachment  is  in  no 
way  affected  by  the  centering  of  the  attached  lens  itself,  as  this  is  capable  of  perfect 
adjustment.  The  only  way  in  which  error  can  occur  is  through  the  imperfection  of 
the  objective  tube.  If  the  cylindrical  surface  of  the  object-head  of  the  telescope  on 
which  the  attachment  is  placed  is  not  concentric  with  the  optical  axis  of  the  teles- 
cope this  error  will  enter  into  the  adjustment  of  the  attached  short  focus  lens.  This 
error,  however,  is  never  large  on  an  instrument  sent  out  by  our  firm.  But  even 
admitting  that  there  may  be  some  error  here,  it  must  be  rememembered  that  this  lens 
is  never  used  for  objects  more  than  about  6  feet  away  ;  consequently  the  resulting 
error  on  the  point  is  entirely  negligible,  and  the  convenience  of  the  attachment:  'n 
many  cases  is  so  great  that  it  entirely  outweighs  any  such  consideration,  since  the 
work  done  at  this  distance  will  be  entirely  consistent  with  the  work  done  with  the 
instrument  on  the  longer  distances.  The  attachment  fills  a  want  that  has  long  been 
felt  by  engineers  and  is  certainly  a  step  in  advance  in  the  perfection  of  instruments  of 
precision. 

To  attach  this  device  to  their  old  instruments  it  will  be  necessary  to  send  the  instru- 
ment to  them,  as  every  lens  attachment  must  be  specially  fitted  and  centered.  How- 
ever, it  can  be  supplied  with  any  of  their  new  instruments,  either  Transits  or  Levels, 
made  since  1899. 

When  attached  to  transits,  No.  1  permits  focusing  objects  to  about  3£  feet,  No.  2 
permits  focusing  objects  to  about  2^  feet  :  both  permit  focusing  objects  to  about  2  feet 
from  center  of  instrument. 

This  is  so  important  a  feature  that  one  trial  will  convince  one  that  it  is  indispensa- 
ble to  the  outfit  of  an  engineer  The  device  is  patented.  The  Messrs.  Berger 
are  also  prepared  to  attach  it  to  their  Wye  and  Dumpy  level,  lor  focusing  nearly  aa 
close  as  stated  above  for  transits.  For  pi-ices  see  catalogue,  page  203. 


102 

NOTE. 

In  selecting  instruments  from  catalogues,  engi- 
neers should  not  be  led  so  much  by  a  simple  com- 
parison of  prices,  as  by  the  advantage  offered  in 
superior  merits,  working  capacity,  and  preservation 
of  fine  qualities  in  case  of  severe  treatment.  We  can 
cite  instances,  where  transits  and  levels  of  our  man- 
ufacture had  severe  falls,  resulting  without  injury  to 
any  part  of  instrument  —  not  even  disturbing  the 
adjustments. 

A  larger  outlay  of  $1O  or  $2Q  in  the  purchase 
of  a  superior  article  is  a  great  saving  in  time  and 
expense  in  the  end. 

Owing  to  the  great  variety  of  styles  and  combina- 
tions enumerated  with  our  instruments  (which  com- 
binations may  easily  be  carried  into  the  hundreds)  the 
principal  combinations  only  are  provided  for  in  the 
code  at  the  back  of  the  catalogue  and  Code  names 
underlined  indicate  customary  instruments  which  we 
intend  to  carry  in  stock.  A  large  stock  of  these  instru- 
ments is  kept  on  hand,  but  owing  to  the  very  many 
combinations  of  sizes  and  styles  and  to  the  great  de- 
mand, at  times  the  instruments  desired  may  have  to  be 
made  specially,  nevertheless.  It  is  therefore  advisable 
to  order  all  instruments  as  far  as  possible  ahead  of  the 
intended  for  their  use. 


-  CABLE- 3£AG£f<-  BOSTON- 


LABORS  £.T   VJRTVTE 

M  [•       •    .-  ,.•.•.•.•  I  i          .       i  •   r-.  '"'ink  ^J 


ESTABLISHED 


Jc)7J 


LIST  AM© 


OF 

INSTRVTUENTS 

OF  PRECISION    FOR 
SVRVEYORS 

ENGINEERS 
AND  ASTRONOMERS 

MADE    BY  i 

CLBERGERfrSONS 

BOSTON,  MASS. 


RIBBING  PARTS  OF  INSTRUMENTS. 


Patrons  will  notice  the  omission  in  this  edition 
of  illustrations  of  the  practice  of  ribbing  and  con- 
struction of  parts  of  our  instruments  to  gain  strength 
and  lightness. 

We  omit  the  illustrations  of  these  improvements, 
introduced  by  us  since  1871,  because  now  they  are 
in  common  use. 

The  cuts  in  this  catalog  show  the  lines  on  which 
we  are  advancing  these  improvements  to  an  extent 
hitherto  unknown. 


ALUMINUM. 

We  omit  cuts  in  former  editions  of  parts  of  in- 
struments made  of  aluminum  alloys,  because  said  cuts 
do  not  express  the  wider  range  of  use  to  which  these 
alloys  are  being  applied  by  us  today  to  instruments  of 
special  design  for  special  purposes. 

Nevertheless,  in  the  present  state  of  these  alloys 
it  is  incumbent  upon  us  to  say  that  the  opinion  ex- 
pressed in  Part  I  of  this  catalogue  must  still  gener- 
ally be  adhered  to. 

These  alloys,  in  the  construction  of  field  instru- 
ments, must  be  used  with  extreme  caution  and  judg- 
ment to  give  satisfaction. 

104 


G-        » 


H 


The  Berber  Complete  Engineers'  and  Surveyors'  Transit  No,  Ic. 

For  description  and  prices  see  Engineers'  and  Surveyors'  Transit.   ; 


The  Berger  Complete  Mine  Transit  No.  4. 

With  Style  I  interchangeable  auxiliary  telescope. 
(Horizontal  circle  either  4  or  4>£  inches.) 

For  description  and  prices  see  Mine  Transits. 


[Patented) 


The  Berber  Complete  Mine  Transit  No.  4k. 

With  edge  graduations  and  fully  enclosed  vertical  circle. 

For  description  and  prices  see  Mine  Transits. 


115 


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Spirit  Levels. 


For  the  benefit  of  our  patrons  we  enumerate  below  the  principal  Spirit  Levels  we  are  prepared  to  supply 
at  short  notice.  They  are  made  by  us,  and  are  of  the  same  superior  quality  as  those  furnished  with  our  instru- 
ments. In  the  list  below  we  give  length,  diameter,  and  degree  of  sensitiveness.  They  are  graduated,  as  a 
rule,  as  shown  above.  —  Levels  different  in  size  from  this  list  can  be  made  to  order  only,  and  will  be  furnished 
only  when  order  is  accompanied  with  the  tube  or  mounting  for  which  one  is  intended,  and  also  stuting  the 
kind  of  instrument  it  is  for,  and  the  degree  of  sensitiveness  desired.  We  will  positively  not  make  any  levels 
upon  written  dimensions  only,  but  require  the  tube  to  be  sent  in  all  cases,  as  otherwise  we  will  not  be  respon- 


sible 
WO. 

2. 
3. 
4. 
5. 

6. 
7. 

8. 

or  any  failure  in  that  re 
Length  from  tip  to 
tip  in  Inches. 
6.50  to  6.60 
4.75 
4.10 
300 
2.40 
2.00  to  2.25 
1.68    - 

spect.     Please  read  paj 
Diameter  in  Inches. 

0.75  to  0.80 
0.65  to  0.68 
0.58  to  0.60 
0.51  to  0.53 
0.51  to  0.53 
0.41  to  0.43 
0.41  to  0.43 

jes  6  and  15. 
Sensitiveness. 

One  div.  (0.10)  =  10"  to  20"  of  arc 
(0.15)  =15"  to  20"       '• 
(0.15)  =15"  to  20"       ' 
(0.10)  =20"  to  25"       ' 
(0.10)  =60" 
(0.10)  =  70" 
(0.10)  =  75" 

Price  mounted, 
if  tube  is  re- 
turned. 
$4.50  to  5.00 
3.50  to  4.00 
3.80 
3.20 
1.80 
1.80  - 
1.80 
Price 
unmounted, 
50  cents  less. 

Mi 

C.  L.  Berger  &  Sons'  Quick  Leveling  Attachment. 

Shown  as  applied  to  Lercl*  and  Transits. 

(See  page  45  of  Manual.) 

Code  Word  Entroba  for  use  with  Transit  No.  4  $2O.OO 

Epilobium  for  all  other  sizes 15.OO 


119 


Code  word    .    .    Oakadum. 

Spirit-Level  on  Metal  Base. 

Ground  Spirit-Level,  one  division  of   level  about  20  sec.  of  arc ;  mounted  on 
8-inch  metal  base,  provided  with  a  handle.  Level  adjustable.    In  case. 

Price,  $14.OO 

These  levels  are  extensively  used  in  machine  shops  for  leveling  up  and  testing 
fine  machinery,  etc.,  also  used  for  leveling  up  apparatus  in  observatories,  physical  and 
chemical  laboratories,  and  for  setting  weirs,  etc. 


Code  Word 


Oakesia. 


Brass  or  nickel-plated. 


Locke's  Hand-Level. 

In  case         


Price     $8.OO 


NOTE.— This  consists  of  a  brass  tube  6  inches  long,  with  a  small  level  mounted  on  its  top  to  the  left  of  its 
center  near  the  object  end.  Underneath  the  level  is  a  horizontal  wire  stretched  upon  a  frame.  This  frame  is 
made  adjustable  by  a  screw  and  a  spring  working  against  each  other,  or  by  two  opposing  screws  placed  at  the  ends 
of  the  level  mounting.  In  the  tube  directly  below  the  level  is  placed  a  totally  reflecting  prism,  acting  as  a  mirror 
set  at  an  angel  of  45°  to  line  of  sight.  The  images  of  the  bubble  and  wire  are  thus  reflected  to  the  eye. 
The  prism  divides  the  aperture  in  two  halves,  in  one  of  which  is  seen  the  bubble  and  wire  focussed  sharply  by 
a  convex  lens  placed  in  the  draw  tube,  while  the  other  permits  of  an  open  view.  Putting  the  instrument  to 
the  eye  and  raising  and  lowering  the  object-end  until  the  bubble  is  bisected,  natural  objects  can  be  seen  through 
the  open  half  at  the  same  time,  and  approximate  levels  can  then  be  taken.  To  prevent  dust  and  dampness 
from  entering  the  main  tube,  both  the  object  and  the  eye  ends  are  closed  up  with  plain  glasses.  la  preliminary 
work  this  is  a  very  useful  instrument. 


Hand-Level  and  Clinometer. 
Abney  Level  and  Clinometer.  Price  $14.OO. 

NOTE.  —  This  instrument  is  similar  to  the  Locke's  hand-level,  but  the  small  spirit  level  mounted  on  top 
can  be  moved  in  the  vertical  plane  and  clamped  to  a  dial  graduated  in  single  degrees,  thus  the  angles  of  slopes, 
etc.,  can  be  measured  also. 

Code  Word    .    .    .    Oleander. 


120 


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19.1 


Tripods  for  the  Engineers'  and  Surveyors'  Transits 

and  Levels. 

For  description  see  page  7;  for  prices  and  weights,  if  extra  ones  are  desired,  see 
preceding  page. 


122 


123 

C.  I,.  BKRGEK  &  SONS.  BOSTON 


Road  Builder's 
MONITOR  TYPE  DUMPY  LEVEL. 


A  sturdy,  compact  instrument  of  smaller  size  and  less  weight  than  our 
14^"  Monitor  Type  Dumpy  L,evel. 

This  instrument  has  been  designed  by  us  to  meet  a  growing  want  for  the  high- 
way as  well  as  for  the  Drainage  Engineer.  The  degree  of  accuracy  obtained  with 
it  is  commensurate  with  the  work  required.  The  telescope  is  erecting  and  has 
lenses  of  perfect  definition  with  a  large  flat  field  of  view  and  is  balanced  from  the 

center  with  Sunshade  attached.  The  eye-piece  cap  is  large  in  diameter  and  made  so 
that  it  affords  a  protection  to  the  observer's  eye  in  a  glaring  sun.  It  has  been  com- 
bined with  a  dust-guard  which  fully  protects  the  eye-piece  focussing  slide. 

The  spirit  level  is  very  sensitive  and  is  mounted  on  top  of  the  telescope.  It  is 
protected  by  a  revolvable  tube  to  act  as  a  guard  to  prevent  breakage  when  not  in  use. 

The  leveling  head  is  of  a  single  casting  of  improved  form,  so  that  the  center  will 
not  bind  in  the  socket  from  any  strain  exerted  by  the  four  leveling  screws  which  lat- 
ter are  protected  from  injury  and  dust. 

We  have  adopted  for  this  level  Our  standard  long  stout  center  with  which  all  of 
our  instruments  have  been  identified,  thus  adding  to  its  Stability. 

This  level  will  withstand  rough  treatment.  The  adjustments  are  few,*  —  when 
once  made  they  are  lasting  — and  above  all  the  instrument  is  dependable  at  all  times 
and  free  from  any  tremor  even  in  a  strong  wind.  Its  rounded  forms,  together  with 

the  fine,  dark  and  durable  wear  resisting  leather  finish  applied  to  the  exterior 
surfaces,  appeal  to  anyone  in  sympathy  with  advanced  instrument  design. 

SPECIFICATIONS :  — 

Telescope  Erecting"  12  inches  long,  aperture  15i",  power  24  dia.  Focuss- 
ing slide  very  long  and  provided  with  a  dust  guard. 
Eye-piece  with  large  flat  field  of  view,  provided  with  an  improved  screw 

arrangement  permitting  to  focus  the  wires  by  simply  turning  its  head  slightly 

to  right  or  left. 
Spirit  Level  5%  inches  long  between  centers  of  suspending  arms.    The  spirit 

level  is  very  sensitive  and  accurately  ground  to  a  true  curvature  and  barrel 

shape. 
Center  of  hard  bell  metal. 

Mahogany  box  provided  with  strap,  lock,    and  hooks,    contains  sunshade 

wrench,  scre\vdriver  and  adjusting  pins. 

Weight  of  Instrument  7  Ibs.     Weight  of  tripod  about  9  Ibs. 

Gross  weight  of  instrument  securely  packed  for  shipment  in  two  boxes  about 

35  Ibs. 
Code  word:  Oleaster.  Price  as  above  $75.OO 

Extras  to  12"  Monitor  Type  Dumpy  Level. 

Stadia  Wires  fixed  in  ratio  1 : 100 *3.oo 

Gossamer  water-proof  bag  to  protect  the  instrument  in  case  of  rain  or  dust  i.oo 
Bottle  of  fine  watch-oil  to  lubricate  the  lever  center  ....  .35 


* — The  above  instrument,  being  of  the  Dumpy  level  type,  has  to  be  adjusted  by  the  two  peg 


14 


124 
C.  L,.  BEKGEK  &  SONS.  BOSTON 

111  MONITOR  TYPE  DUMPY  LEVEL. 

2  Tubular  Bar 


A  sturdy,  compact  instrument  of  precision.  For  use  in  the  Army,  about  For- 
tifications, in  Cities,  Construction  of  Highways,  Railroads,  Tiiimels,  Mines, 
and  about  Factories,  etc.,  where  a  smaller  size  and  less  weight  is  desirable. 

In  answer  to  many  inquiries  for  a  Dumpy  Level  to  take  the  place  of  the  frail 
and  often  badly  designed  14  inch  wye  Levels,  commonly  found  on  the  market,  we 
are  offering  this  most  advanced  type. 

The  Monitor  Type  Dumpy  Level  is  made  to  last,  its  vital  parts  are 

strongly  built  in  a  stubby  style.  The  center  flange  and  the  clamp  and  tangent  screw  are 
carried  up  very  far  into  the  hollow  bar  thus  reducing  the  height  of  instrument  to  the 
tripod  head  and  are  protected  from  rain,  dust,  grit  and  injury.  All  this  has  been  ac- 
COmplished  without  sacrificing  the  standard  long  center  with  which  all  of  our  in- 
struments have  always  been  identified,  thus  adding  to  the  stability  of  the  instrument. 
The  hollow  bar  is  tubular  in  form  and  therefore  is  deflection  resisting.  A  far  greater 
amount  of  rigidity  will  be  found  in  the  Monitor  type  level  bars  which  are  greatly 
superior  to  those  of  the  older  familiar  forms  of  same  weight.  These  bars  are  not 
affected  by  temperature  changes  owing  to  the  free  circulation  of  air  through  and 
around  the  bar. 

The  telescope  tube  is  made  of  a  single  casting  and  bored  out  to  be  truly  cylindrical 
(not  made  of  tubing,  which  is  often  Oval  in  form,  See  page  128).  The  leveling  head 
is  also  of  a  single  casting  of  improved  form,  so  that  the  center  will  not  bind  in  the 
socket  from  any  strain  exerted  by  the  four  leveling  screws.  Owing  to  the  peculiar 

construction  of  the  socket  the  center-clamp  screw  cannot  exert  any  pressure  upon 
the  center  after  the  instrument  is  clamped  to  the  socket,  thus  leaving  the  bubble 
undisturbed. 

This  Level  will  Avithstand  all  kinds  of  rough  treatment  when  transported  On  mule- 

back,  over  mountains,  impassable  roadsor  throughthe  wilderness.  The  adjustments 

are  few, — when  Once  made  they  are  lasting  —  and  above  all  the  instrument  is  de- 
pendable at  all  times  and  free  from  any  tremor  even  in  a  strong  wind.  Its  rounded 

forms,  together  with  the  fine,  dark  and  durable  wear  resisting  leather  finish  applied 
to  the  exterior  surfaces,  appeal  to  anyone  in  sympathy  with  advanced  instrument 
design.  The  telescope  is  erecting. 

SPECIFICATIONS:— 

Telescope  Erecting1  14#  inches  long,  aperature  1^,  power  30  dia. 

Focussing  slide  very  long  and  provided  with  our  collapsible  dust  guard,  see 
page  128. 

Eye-piece  with  large  flat  field  of  view,  provided  with  an  improved  screw 
arrangement  permitting  to  focus  the  wires  by  simply  turning  its  head  slight- 
ly tO  right  Or  left.  The  eye-piece  cap  is  large  in  diameter  and  made  so  that  it 
affords  a  protection  to  the  observer's  eye  in  a  glaring  sun.  It  has  been  combined 

with  a  dust-guard  which  fully  protects  the  eye-piece  focussing  slide. 
Spirit   Level  O  inches  long  between  centers  of  suspending  arms.  The  spirit 

level  is  very  sensitive  and  accurately  ground  to  a  true  curvature  and  barrel 

shape. 

Center  of  hard  bell  metal. 
Clamp  and  Tangent  Screw. 

Mahogany  box  provided  with  strap,  lock,  and  hooks,  containing  sunshade, 

wrench,  screwdriver  and  adjusting  pins. 

Weight  of  instrument  9/2  Ibs.     Weight  of  tripod  about  9  Ibs. 

Gross  weight  of  instrument  securely  packed  for  shipment  in  two  boxes  about 

40  Ibs. 
Code  word :  Alodol  Price  as  above  $  1 15 

Extras  to  14^  inch  Monitor  Type  Dumpy  Level. 
Stadia  Wires  fixed  in  ratio  1 :  100 *:J.oo 

Steel  Center  running  in  a  cast  iron  socket  to  insure  freest  motion  with 

perfect  fit 10.00 

Fine  mirror  mounted  in  case  with  universal  joint.  (This  is  readily  at- 
tachable to  either  side  of  the  instrument  and  facilitates  the  reading 
of  the  bubble  on  soft  ground  without  stepping  aside)  .  .  .  10.00 

Gossamer  water-proof  bag  to  protect  the  instrument  in  case  of  rain  or  dust          i.oo 

Bottle  of  fine  watch-oil  to  lubricate  the  lever  center  ....  .35 


MONITOR  TYPE  DUMPY  LEVEL. 

Inverting  Telescope.  Aperture,  Power  and  Price  same  as  above.  For  descrip- 
tion and  cut  see  pages  126-127.    (Code  word:  Abardo.) 


C.  I,.   UKKGKJl  &  SONS.    BOSTON 


r 
H 

i  r 

*    2 


5     "* 


£   § 

i   H 


}  if  if 

IM  s 

!  1 5  ? 
I?      ? 


14 


Code  Words  for  14^  iiu-h  Dumpy  levels, 

inch  erecting  telescope  ........ 

inch  erecting  telescope  with  fixed  stadia  wires 


Alodol 
Abadc'iio 


C.  t.  BKKGER  &  SONS. 


1 5"  AND  1  7|"  MONITOR  TYPE  DUMPY  LEVEL. 

An  instrument  of  great  precision,  superior  to  any  Wye  Level  of  same,  aperture, 
power  of  telescope,  and  same  sensitiveness  of  spirit-level.  The  best  instrument  for 
use  in  distant  lands  and  rough  country  on  account  of  its  great  compactness, 
simplicity,  strength  to  withstand  rough  treatment,  permanency  of  adjust- 
ments,  and  steadiness  in  a  strong  wind,  requiring  but  ordinary  attention  and 
care  to  keep  in  working  order.  For  a  fuller  description,  see  page  128. 

This  new  type  of  Dumpy  Level  with  round,  hollow,  and  very  long  cross-bar,  must 
be  considered  the  most  perfect  in  this  line.  It  stands  low  on  the  tripod,  and  its  fine 
spirit-level,  being  placed  in  the  hollow  cross-bar,  below  the  telescope,  can  be  read  from 
either  side,  and  is  entirely  protected  from  accident  and  liability  to  derangement  of  ad- 
justments, also  from  the  disturbing  influences  of  the  heat  of  the  sun,  touch  of  fingers, 
breath,  etc.  —  These  latter  conditions  are  not  fulfilled  in  instruments  where  the  level  is 
placed  on  top  or  at  the  side  of  the  telescope,  and  are  frequently  causes  of  the  incorrect 
reading  of  the  bubble. — This  instrument  is  of  very  strong  build,  combined  with  a  mini- 
mum of  weight,  and  as  it  consists  of  a  fewer  number  of  pieces  than  the  Wye  Level,  is 
less  liable  to  derangement  in  case  of  accident.  The  adjustment  once  properly  made  by 
the  two  peg  method  (see  adjustment  of  Dumpy  Level,  page  63)  is  apt  to  stay  so  for 
years,  thus  removing  one  of  the  chief  objections  as  compared  with  those  of  a  Wye 
Level.  In  making  the  adjustment  of  this  Dumpy  Level  the  engineer  does  not  depend 
so  much  on  mechanical  perfection,  as  on  his  own  superior  skill  and  sense  of  accuracy. 

To  meet  an  urgent  demand  this  type  of  Dumpy  Level  is  now  provided  with  a 
clamp  and  tangent  screw  to  enable,  in  a  strong  wind,  to  keep  the  telescope  upon  an 
object,  and,  although  it  raises  the  price,  it  will  prove  an  invaluable  accessory,  well 
worth  the  extra  cost.  This  instrument  is  leather-finished. 

The  telescope  can  be  inverting  or  erecting;  see  cuts  on  pages  127  and  129. 
The  objective  in  either  case  will  have  the  same  aperture. 

We  recommend  this  instrument  highly  for  all  work  of  a  high  character,  such  as 
bench  leveling,  water-works,  railroad  construction,  also  for  reconnoissance. 

SPECIFICATIONS :  — 

Inverting  15  inch  long,  aperture  1^,  power  28  dia. 
Erecting  17 %  inch  long,  aperture  1^,  power  32  dia. 
Focussing  slide  very  long  and  provided  with  a  dust  guard  when  run  out  for  sights 
as  near  as  about  12  feet. 

Eye-piece  with  large  flat  field  of  view,  provided  with  an  improved  screw 
arrangement  permitting  to  focus  the  wires  by  simply  turning  its  head  slightly 
to  right  or  left. 

Spirit  Level  7 '  ^  inches  long  between  centers  of  suspending  arms.     The  spirit 
level  is  very  sensitive  and  accurately  ground  to  a  true  curvature  and  barrel  shape. 
Center  of  hard  bell  metal  is  cast  in  one  piece  with  the  hollow  cross  bar. 
Clamp  and  Tangent  Screw 

Mahogany  box  provided  with  strap,  lock,  and  hooks,  containing  sunshade,  wrench, 
screwdriver  and  adjusting  pins. 

Weight  of  instrument  10  Ibs.     Weight  of  tripod  about  10  Ibs. 
Gross  weight  of  instrument  securely  packed  for  shipment  in  two  boxes  about  50  Ibs. 
Codeword:  15  inch  inverting  telescope  Abardo 

"       "       17fc"  erecting          "         Aciiia       Price' each  as above' $115 
(For  Code  Words  of  Extras  below,  see  page  B  of  complete  code  at  back.) 

Extras  to  ±5"  and  !71/£"  Dumpy  Levels. 

Stadia  Wires  fixed  in  ratio  1:  100        .  ...        $3.OO 

Steel  Center  running  in  a  cast  iron  socket  to  insure  freest  motion  with 

perfect  fit,  see  page  134.      (Made  to  order  only.)  1O.OO 

For  quick  leveling  attachment  see  page  118.  .  .  •         15.OO 

Fine  mirror  mounted  in  case  with  universal  joint.  (This  is  readily  attach- 
able to  either  side  of  the  instrument  and  facilitates  the  reading  of  the 
bubble  on  soft  ground  without  stepping  aside)  .  .  .  1O.OO 

Gossamer  water-proof  bag,  to  protect  the  instrument  in  case  of  rain  or  dust  l.OO 

Bottle  of  fine  watch-oil  to  lubricate  the  level  center  .35 

A  detachable  Vernier  Compass,  with  variation  setoff  E  &  W  and  with  3'/£ 
inch  needle,  can  be  mounted  on  top  of  these  Dumpy  Levels  at  an  extra  expense 
of  $16.OO.  Made  to  order  only. 


127 

C.  L.  BEKGEH  &  SONS. 


5     S- 


Code  Words  for  Dumpy  Levels. 

16-inch  Inverting  Telescope 

J5-in"h  Inverting  Telescope  with  fixed  stadia  wires  . 


Abardo 
Abella 


(For  Extras  and  changes  from  Abardo  and  Abello  see  page  B  of  complete  code  at  back,) 


C. 


1-28 
BEKGEU  &  SONS. 


Monitor  Type  Dumpy  Level. 

Additional  Information  pertaining  to  its  mechanical  Construction. 

From  the  illustrations,  pages  127,  129,  it  will  be  seen  that  the  mechanical  parts  of 
this  Dumpy  Level  are  few  and  can  easily  be  made  to  be  mechanically  correct,  and  that 
there  are  no  working  strains  whatever  in  the  metal  to  exert  an  undue  influence  upon  the 
adjustments  with  changes  of  temperature. 

The  telescope  barrel  and  both  uprights  are  cast  in  one  piece  of  hard  composition 
metal;  and  in  order  to  arrive  at  a  high  degree  of  accuracy  the  barrel  is  bored  out  to  be 
truly  cylindrical,  a  condition  never  attained  by  the  use  of  drawn  tube.  (For  reasons 
mentioned  later  both  ends  of  the  outside  tube  are  slightly  larger  in  diameter,  forming 
collars  turned  truly  concentric  to  the  bore,  serving  in  principle  the  same  object  as  collars 
of  a  Wye  Level  telescope.)  This  being  accomplished,  the  bottom  surface  of  the  uprights 
is  turned  truly  parallel  to  the  bore.  The  strongly-ribbed  cross-bar  and  instrument  center 
are  cast  in  one  piece  of  hard  bell-metal.  At  the  time  when  the  center  about  which  the 
instrument  revolves  is  fitted  to  its  socket,  the  resting-places  for  the  uprights  are  also  turned 
off  so  as  to  be  truly  at  right  angles  to  it,  from  which  follows  that  the  geometrical  axis  of 
the  telescope  barrel  when  latter  is  placed  upon  them  must  also  be  at  right  angles  to  the 
center.  The  level  casing,  too,  is  a  casting.  The  spirit-level  itself  is  fastened  into  this  cas- 
ing by  a  superior  method  to  preclude  any  strain,  so  that  its  true  form  may  "be  preserved, 
The  focusing  slide  is  the  only  tube  made  of  brass,  turned  and  closely  fitted  in  the  lathe. 

In  adjusting  this  instrument  in  the  shop  it  is  treated  like  a  Wye  Level.  The  collars 
at  the  end  of  the  telescope  barrel  serve  to  adjust  the  cross-wires  for  collimation  by  revol- 
ving the  telescope  in  wyes.  When  this  is  accomplished  the  telescope  barrel  with  its  attached 
level  is  then  firmly  screwed  to  the  cross-bar.  The  next  step  in  the  shop  is  to  adjust  the  spirit- 
level  to  the  line  of  collimation  as  described  elsewhere.  This  being  done,  the  adjuster 
in  the  shop  now  proves  whether  the  geometric  and  optical  axes  of  the  telescope  are  really 
in  the  horizontal  plane  by  revolving  the  instrument  180°  on  its  center;  should  the  bubble 
remain  in  the  middle  of  its  tube  it  must  be  assumed  that  it  is;  however,  if  not,  he  touches 
one  of  the  uprights  off  until  it  does.  As  a  rule  the  mechanical  work  is  so  correct  that 
the  geometric  and  optic  axes  coincide  within  a  few  division  marks  of  the  graduated  level, 
requiring  but  a  very  few  strokes  with  a  fine  file  for  final  adjustment. 

From  the  foregoing  it  will  be  seen  that  a  leveling  instrument  so  constructed,  barring 
severe  accidents,  must  hold  its  adjustments  for  years,  and  that  all  subsequent  verifications 
of  the  line  of  collimation  in  the  field  by  the  two  peg  method  must  be  made  by  the  Engi- 
neer by  slightly  moving  the  cross-wires,  and  that  the  adjustment  of  the  spirit-level  is 
to  be  made  in  the  customary  manner  by  simply  turning  the  instrument  180°  on  its  center. 
An  instrument  so  constructed  needs  but  little  care  and  therefore  is  better  adapted  to 
rough  usage  (to  which  it  is  subject  at  times)  since  its  simplicity  ensures  greater  free- 
dom from  derangement. 

The  Dumpy  Level  described  above  must  stand  as  an  example  of  good  practice. 
Many  Engineers  prefer  it  to  an  ordinary  Wye  Level.  The  prevailing  mistrust  can 
generally  be  traced  to  the  use  of  cheap  commercial  Dumpy  Levels.  The  above  infor- 
mation as  to  the  method  of  construction  in  the  shop  has  been  given  at  great  detail  tr»  eho\v 
that  this  instrument  may  well  rank  with  the  best  wye  levels. 

(For  Price  of  this  Instrument  and  Extras  see  page  126.) 


Berber's  Collapsible  Dust  Guard 


This  feature  as  shown  below  is  furnished  with  the  14,  lo  and  1  7>2  inch  3Ioiiitor 
Type  Dumpy  Levels  and  protects  the  telescope's  focussing  slides  almost  com- 
pletely from  grit  and  water  within  their  entire  range. 


TELESCOPE  BARREL- 


C.L.BE.RGERiSON3   BOSTON  MA5S.U.5.A. 


EXTENDED 


CONTRACTED 


129 

C.  L,.  BEIIGKR  &  SONS, 


Code  AVorcls  for  Dumpy  Levels. 

-inch  erecting  telescope 

-inch  erecting  telescope  with  fixed  stadia  wires    . 


Aciiia 
Actus 


(For  Extras  and  changes  from  Acnia  and  Actus  see  page  B  of  complete  code  at  back.) 


18 


130 

The  Berger 
MONITOR  TYPE  WYE  LEVEL. 


A  combination  of  our  Dumpy  and  Wye  Levels,  see  pages  12&-135. 
For    close    bench    leveling    and    construction    work 
whether  used  on  the   surface    or     underground. 

Essential  features  :-  Compactness  with  great  strength  as  exemplified  in  our 
Dumpy  Level,  to  resist  severe  treatment  in  rough  country  work.  Protection  of 
spirit-level  and  collars,  thereby  securing  increased  accuracy,  efficiency  and 
greater  permanency  of  adjustment. 

In  this  new  type  of  instrument  the  adjustment  of  the  line  of  collimation  of  the  tele- 
scope  and  telescope  level  is  made  in  the  same  manner  as  that  in  the  regular  Wye 
Level,  but  to  prevent  the  wear  on  the  collars  and  to  secure  compactness,  it 
differs  from  that  insofar  as  the  telescope  can  only  be  revolved  in  the  wyes  about 
20  to  30°  to  permit  of  the  lateral  adjustment  of  the  spirit-level,  so  as  to  reduce  the 
wear  on  the  collars  to  a  minimum.  The  line  of  collimation  of  the  telescope  needs 
to  be  verified  only  at  times  by  lifting  the  latter  out  of  its  wyes  after  bi-secting  a 
point  and  then  replacing  it  with  the  telescope  rotated  180°,  to  have  level  now  up 
thereby  securing  the  same  condition  as  where  the  telescope  is  revolvable  in  the 
wyes. — It  is  a  well-known  fact  that  the  wear  on  the  collars  where  the  telescope  is 
revolvable  is  often  so  marked  that  their  equality  of  diameter  and  true  form  can- 
not be  depended  on,  and  therefore,  while  the  instrument  apparently  is  in  adjust- 
ment it  may  be  very  much  out.  The  only  course  left  open  in  such  a  case  is  to  treat 
the  instrument  like  a  Dumpy  level  and  to  adjust  the  level  to  the  telescope  by  the 
two-peg  method. 

The  Spirit-level  guarded  by  the  telescope  and  by  a  double  casing  formed  as  it  were 
by  the  protection  at  the  sides  raises  it  to  the  standard  of  a  glass-protected  level 
vial  shown  in  the  Precise  Levels  described  later  on,  but  without  the  detriment  com- 
mon to  the  latter  devices  when  films  settling  on  the  inaccessible  vial  and  inner 
surfaces  of  such  a  protecting  glass  cover  impair  the  reading  of  the  bubble.  To  fully 
protect  this  level  vial  from  sun  and  rain  at  times,  or  in  underground  work  from 
smoke  and  gases  a  thin  piece  of  transparent  celluloid  over  the  exposed  part  of  the 
vial  and  held  in  place  by  the  sides  of  the  cross-bar,  will  accomplish  the  same  end, 
and  it  can  be  cleaned  and  renewed  at  will,  thus  securing  to  this  instrument  and  its 
spirit-level  all  the  advantages  possessed  by  our  precise  levels,  at  a  very  low  cost. 
Size,  power  and  all  other  particulars  are  like  those  of  our  regular  18"  Engineer's 
Wye  Level,  page  134,  but  it  is  almost  entirely  finished  in  our  superior  and  dura- 
able  leather  finish,  securing  permanency  of  adjustment  and  presenting  a  very  fine 
external  appearance. 

SPECIFICATIONS :  — 
Telescope.    Objects  erect,  aperture  1  ^  inch,  power  35  dia.  Focussing  slide, 

very  long  and  fully  protected  by  dust  guard.  Collars  hard  bell  metal. 
Eye-piece  with  large  flat  field  of  view,  provided  with  an  improved  screw  arrange- 
ment permitting  to  focus  the  wires  by  simply  turning  its  head  slightly  to  right  or 
left.    Line  of  collimation  correct  for  all  distances.    Telescope  balanced  each 
way  from  center  when  focussed  for  a  mean  distance  with  sunshade  attached,  to 
secure  highest  accuracy  attainable.  Stop  provided  so  that  the  cross  wires  will 
always  be  horizontal  and  vertical  in  instrument. 
Spir it-Level  8fi  inch  (between  centers  of  supporting  arms)  level  vial  accurately 

ground  to  a  true  curvature  and  barrel  shape. 

Center  hard  bell  metal  (very  large  in  dia.  and  long,  strong  and  unyielding). 
Mahogany  box  provided  with  strap,  lock,  and  hooks,  contains  sunshade,  wrench, 
screwdriver  and  adjusting  pin. 

Weight  of  instrument  11  Ibs.     Weight  of  tripod  about  10  Ibs. 
Gross  weight,  securely  packed  for  shipment  in  two  boxes,  about  55  Ibs. 

Code  word,  Acway  Price,  as  above,  14O.OO 

Extras  to  Monitor  Type  Wye  Levels. 

Steel  center  running  in  a  socket  of  cast  iron,  to  insure  freest  motion  with  perfect  fit  S15.0O 

Stadia  wires,  fixed 3.0O 

Short  focus  lens  (see  pages  101,  203),  one  $8.50  .  .  .  per  pair  16.00 
Fine  mirror  with  universal  joint  readily  attachable  to  either  side  of  the 

instrument,  facilitating  the  reading  of  the  bubble  without  stepping  aside  10.00 

Gossamer  water-proof  hood,  to  protect  instrument  from  rain  or  dust  i.oo 

Bottle  of  fine  watch-oil  to  lubricate  the  level  center .3* 


20i 


in 


MONITOR  TYPE  WYE  LEVEL. 


Aperture  1^  inch,  Power  38  dia. 
Code  word,   Aczell  Price,  as  described  above,  $145.OO 


131 
C.  L.  BEKGER  &  SONS 


ft 

I  I 


Code  Words  for  Monitor  Type  Wye  Levels 

18  inch  erecting  telescope  enumerated  page  130 Ac  way 

inch  erecting  telescope Aczell 


181 


132 
C.  I*.  BERGER  &  SONS,  BOSTON 

MONITOR  TYPE  WYE  LEVEL. 

Tubular  Bar 


The  correct  alignments  and  the  handy  arrangement  of  all  operating  parts  make 
this  type  of  level  a  profitable  investment  in  any  Engineering  Department.  Designed, 
built  and  inspected  with  typical  Berger  thoroughness,  it  can  be  depended  upon  to 
produce  accurate  work  through  years  of  constant  service. 

A  close  inspection  of  the  illustration  will  reveal  a  Wye  level  of  a  different  de- 
sign embodying  many  of  the  features  of  our  standard  types.  The  telescope  is  sup- 
ported most  rigidly  in  the  two  Wyes,  which  are  mounted  unusually  low  on  a  Bar 
which  is  Tubular  in  form  and  practically  "  flexture  resisting'."  This  form  of  Bar 

permits  an  entire  Rotation  of  the  telescope  in  its  Wyes  as  in  our  Engineers  18*  and  14" 

Wye  Levels,  Pages  134—135.  Owing  to  its  peculiar  construction  the  clamp  and  a  good 
part  of  the  spindle  and  its  socket  are  concealed  within  this  Bar  which  not  Only  pro- 
tects  these  parts  from  serious  injury  but  keeps  out  grit  and  other  foreign  matter. 
This  instrument  has  been  reduced  in  height  noticeably  which  gives  it  an  appearance 

Of  great  Compactness.  The  Bar  is  designed  so  that  air-currents  which  are  constantly 
changing  in  temperature  may  pass  freely  through  the  top  and  around  the  Bar.  All  this 
has  been  done  without  changing  the  original  length  of  the  spindle  which  has  iden- 
tified all  Berger  instruments  since  1871,  for  their  wonderful  steadiness  and  freedom 
from  tremor  in  a  high  wind. 

The  levelling  socket  is  very  different  in  design  and  a  vast  improvement  over 
Other  makes.  It  consists  of  a  single  piece  casting  of  most  peculiar  form.  The  cen- 
ter will  not  bind  in  the  socket  from  any  strain  exerted  either  by  the  spindle  clamp 
or  leveling  screws.  When  instrument  is  clamped  the  telescope  and  its  level  remain 
absolutely  undisturbed  owing  to  its  Construction— there  being  a  very  deep  recess 

between  the  center's  socket  and  the  bearing  for  the  center's  clamp.  This  feature  is 
now  in  universal  use  on  our  levels. 

The  telescope  level  is  close  to  the  line  of  coiiimation.  The  eye-piece  and  object 
slides  are  dust  protected  by  guards.  The  cap  of  the  eye-piece  is  large  in  diameter 
to  protect  the  observer's  eye  from  the  sun. 

The    principal   parts   are   treated    with    our   wear  resisting  leather   finish    (see 

page  9)  which  secures  a  lasting  covering  to  a  field  instrument  and  for  fine  appear- 
ance has  no  equal.  This  finish  introduced  by  us  in  1907  is  in  universal  favor. 
Some  small  parts  are  still  lacquered  which  enhance  and  bring  out  more  forcibly  the 

beauty  of  its  constructional  lines. 

SPECIFICATIONS:  — 

Telescope.    Objects  erect,  aperture  1  ^  inch,  power  35  dia.  Focussing  slide, 

very  long  and  fully  protected  by  dust  guard.  Collars  hard  bell  metal. 
Eye-piece  with  large  flat  field  of  view,  provided  with  an  improved  screw  arrange- 
ment permitting  to  focus  the  wires  by  simply  turning  its  head  slightly  to  right  or 
left.    Line  of  coiiimation  correct  for  all  distances.    Telescope  balanced  each 
way  from  center  when  f ocussed  for  a  mean  distance  with  sunshade  attached,  to 
secure  highest  accuracy  attainable.  Stop  provided  so  that  the  cross  wires  will 
always  be  horizontal  and  vertical  in  instrument. 
Spirit-Level  8^8  inch  (between  centers  of  supporting  arms)  level  vial  accurately 

ground  to  a  true  curvature  and  barrel  shape. 

Center  hard  bell  metal  (very  large  in  dia.  and  long,  strong  and  unyielding). 
Clamp  and  Tangent  Screw. 

Mahogany  box  provided  with  strap,  lock,  and  hooks,  contains  sunshade,  wrench, 

screwdriver  and  adjusting  pin. 

Weight  of  instrument  11  Ibs.     Weight  of  tripod  about  10  Ibs. 

Gross  weight,  securely  packed  for  shipment  in  two  boxes,  about  56  Ibs. 

Code  word,  Adacta  Price,  as  above,  14O.OO 

Extras  to  Monitor  Type  Wye  Levels. 

Steel  center  running  in  a  socket  of  cast  iron,  to  insure  freest  motion  with  perfect  fit  Slo.OO 

Stadia  wires,  fixed 3-°° 

Short  focus  lens  (see  pages  101, 203),  one  $8.50           .         .         .           pair  16.OO 
Fine  mirror  with  universal  joint  readily  attachable  to  either  side  of  the 

instrument,  facilitating  the  reading  of  the  bubble  without  stepping  aside  10.00 

Gossamer  water-proof  hood,  to  protect  instrument  from  rain  or  dust  l.oo 

Bottle  of  fine  watch-oil  to  lubricate  the  level  center      .....  .35 


201 


MONITOR  TYPE  WYE  LEVEL. 


Aperture  1>£  inch,  Power  38  dia. 
Code  word,  Adulom  Price,  as  described  above,  $145.OO 


133 

C.  I*  BEHGKK  &  SONS.  BOSTON 


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Code  Words  for  Monitor  Type  Wye  levels 

18  inch  erecting  telescope  enumerated  page  132        .... 


Adacta 


inch  erecting  telescope       ....  e  ....        AclllloUl 


18 


134 

II 


ENGINEERS'  WYE  LEVEL. 

leveling  Instrument  of  Precision. 
For  Fine  Bench  Leveling,  Water-works,  Railroad  Construction,  etc. 

Instrument  has  the  strong,  liollow  and  long"  cross-bar,  introduced  by  us  in 
1871,  mounted  upon  which  are  the  wyes  supported  by  adjust  ing  nuts  of  large  diameter, 
which,  together  with  the  long"  center  also  of  larjre  diameter,  gives  the  necessary 
stability  to  withstand  rough  treatment.  To  secure  compactness  the  telescope  and 
level  tube  are  close  together  (to  protect  latter  from  sun  and  rain),  and,  as  both  are 
close  to  the  cross-bar,  the  instrument  is  steady  in  a  strong  wind.  To  ensure  perma- 
nency of  adjustment,  the  telescope  and  level  mounting  tube  have  our  leather  finish  (see 
page  11),  which  treatment  enables  us  to  combine  many  parts  into  one,  that  would  have 
to  be  screwed  together,  thereby  securing  not  only  great  rigidity,  but  reducing  to  a  min- 
imum the  effect  of  sudden  changes  of  temperature,  and  affording,  a  degree  of  satis- 
faction in  the  field,  secured  in  no  other  way.  This  finish  presents  a  fine  appearance  and 
is  more  durable  than  a  metal  finish.  As  much  depends  upon  the  sensitiveness  of  the 
spirit  level  we  select  this  for  the  character  of  the  field  work,  and,  therefore,  it  ranges 
in  value  in  this  style  of  instrument  from  10  to  20  seconds  of  arc  to  one  tenth  of  one  inch 
of  scale. 

SPECIFICATIONS: 

Telescope.  Objects  erect,  aperture  1 3/8  inch,  power  35  dia.  Focussing  slide* 
very  long  and  protected  by  dust  guard.  Collars  hard  bell  metal  and  of  large 
diameter. 

Eye-piece  with  large  flat  field  of  view,  provided  with  an  improved  screw  arrange- 
ment permitting  to  focus  the  wires  by  simply  turning  its  head  slightly  to  right  or 
left.  Line  of  collimation  correct  for  all  distances.  Telescope  balanced  each 
way  from  center  when  focussed  for  a  mean  distance  with  sunshade  attached,  to 
secure  highest  accuracy  attainable.  Stop  provided  so  that  the  cross  wires  will 
always  be  horizontal  and  vertical  in  instrument. 
Spirit- Level  8)6  inch  (between  centers  of  supporting  arms)  level  vial  accurately 

ground  to  a  true  curvature  and  barrel  shape. 
Center  liard  bell  metal  (very  large  in  dia.  and  long,  strong  and  unyielding). 

Mahogany  box,  provided  with  strap,  lock,  and  hooks,  contains  sunshade,  wrench, 

screwdriver  and  adjusting  pin. 

Weight  of  instrument,  11  Ibs.     Weight  of  tripod,  about  10  Ibs. 

Gross  weight,  securely  packed  for  shipment  in  two  boxes,  about  55  Ibs. 

Code  word  Adlumia.  Price,  as  above,  $  14O.OO 

Extras  to  Engineers'  18"  Wye  Level. 

Steel  center  running  in  a  socket  of  cast  iron,  to  insure  freest  motion  with 

perfect  fit.     (See  cut  on  opposite  page).          ......  815.00 

Stadia  wires,  fixed      .                           ........  3.OO 

Short  focus  lens  (see  pages  101,  203),  one  $8.50         .         .         .         .pair  IG.OO 

Fine  mirror  with  universal  joint  readily  attachable  to  either  side  of  the 

instrument,  facilitating  the  reading  of  the  bubble  without  stepping  aside  10.00 
TCxtra  sunshade  with  smaller  aperture,  for  use  with  the  18-inch  wye  level 

when  the  sun's  rays  are  too  bright  for  accurate  work     ....  1.50 

Gossamer  water-proof  hood  to  protect  instrument  from  rain  or  dust     .         .  l.oo 

Bottle  fine  watch  oil,  to  lubricate  the  level  center         .         .         .         .         .  .35 


14 


ENGINEERS'  WYE  LEVEL. 


Its  essential  features  are  like  those  enumerated  above,  and  shown  in  cut  of   eigh- 
teen-inch  Engineers'  Wye  Level,  with  the  exception  of  size  and  weight.     It  is  de- 
signed for  use  where  a  lighter  instrument  is  desirable.      The    Telescope   has  an 
aperture  of  1  %  inches  and  a  power  of  27  diameter.   The  5^  inch  spirit  level 
is  very  sensitive.    The  center  is  of  bell  metal.    Full  length,  split-leg  tripod. 
Weight  of  instrument,  about  9^  Ibs;  weight  of  tripod,   5^  Ibs. 
Gross  weight  of  instrument,  packed  securely  for  shipment  in  two  boxes,  about  40  Ibs. 

Code  word  Alyssum.  Price,  as  above  $13O.OO 


135 


Oode  Words  for  Wye  levels. 
18  inch  erecting  telescope  enumerated  page  134  (^usual  style)  Adlumia 

U  inch  erecting  teiescope •      AlySSUHl 

(For  I'J.xtras  and  changes  from  Artlmnin  ana  Aiy«8un.  see  page  B  of  complete  code  at  back.) 


136 

18"  HYDROGRAPHER'S  WYE  LEVEL 

Having  a  three-screw*  leveling  base  with  arms  of  greater  radius*  * 
(3-inch)  to  afford  maximum  stability  when  exposed  to  wind  pres- 
sure and  to  better  control  the  spirit  level  of  this  instrument. 

The  instrument  shown  on  opposite  page  has  the  upper  part,  viz:  cross-bar,  telescope 
and  level  exactly  similar  in  size  and  style  to  our  regular  Engineers'  18"  Wye 

Level  (page  134)  except  the  telescope  which  in  this  instrument  is  mostly  of  the  inverting 
kind.— If  an  erecting  telescope  is  desired  we  will  be  pleased  to  furnish  it,  in  which 
case  the  aperture  will  be  the  same  but  the  power  will  be  35  dia.  only. — As  regards  the 
mode  of  securing  the  instrument  to  the  tripod  by  means  of  the  fastener,  see  cut  and  de- 
scription, page  46,  in  article,  "Shifting  Center." 

This  fastener  is  very  simple  and  even  in  the  coldest  weather  easy  to  manipulate. 
It  adds  very  little  to  the  weight  and  secures  the  necessary  stability  in  taking  up  all 
back  lash  of  the  leveling  screws  after  wear.  It  is  better  than  any  other  device 
that  we  know  of  to  achieve  this  end. 

The  tripod  bolts  are  the  same  distance' from  the  center  as  the  leveling  screws. 

Made  to  order  only 

SPECIFICATIONS:— 

Telescope;  objects  inverted,  aperture  1 3/£  inch,  power  40  dia.;  focussing  slide 

very  long  and  protected  by  dust  guard;  collars  hard  bell  metal;  line  of  collima- 
tion  correct  for  all  distances;  telescope  balanced  each  way  from  center  when 
focussed  for  a  mean  distance  with  sunshade  attached  to  secure  highest  accuracy 
attainable;  stop  provided  so  that  the  cross  wires  will  always  be  horizontal  and 
vertical  in  instrument. 

Eye-piece  perfectly  achromatic  with  large,  flat  field  of  view;  provided  with 
an  improved  screw  arrangement  permitting  to  focus  the  wires  by  simply  turn- 
ing its  head  to  right  or  left. 

Center  of  hard  bell  metal  is  large  in  dia.,  long,  strong  and  unyielding. 

Spirit  Level  8^/3  inches  between  centers  of  suspending  arms.  Sensitive  ness  is 
8  to  1O  seconds  of  arc  for  one  tenth  inch  of  the  scale,  (unless  otherwise  spec- 
ified). 

Mahogany  box  provided  with  strap,  lock  and  hooks,  contains  sunshade,  wrench, 
screwdriver  and  set  of  adjusting  pins. 

Weight  of  instrument  about  12  Ibs.  Weight  of  split-leg  tripod  about  ]  3  Ibs. 
Gross  Weight  securely  packed  for  shipment  in  two  boxes  about  60  Ibs. 

Code  name  Andromeda  Price  as  above  $158.OO 

Extras  to  Hydrographer's  Wye  Level. 

Stadia  wires  fixed  ...........       $3.00 

Steel  Center  running  in  a  cast  iron  socket  to  insure  freest  motion  with  per- 
fect fit 15.OO 

Fine  mirror  mounted  in  metal  frame  with  universal  joint.  (This  is  readily 
attachable  to  either  side  of  the  instrument  and  facilitates  the  reading  of 
the  bubble  on  soft  ground  without  stepping  aside).  .....  10.00 

Extra  sunshade  with  smaller  aperture  for  use  with  the  telescope  when  the 

sun's  rays  are  too  bright  for  accurate  work  ......  1.50 

Gossamer  water-proof  bag,  to  protect  the  instrument  in  case  of  rain  or 

dust i.oo 

Bottle  of  fine  oil  to  lubricate  the  level  center 0.35 

Prior  to  1888  we  have  sometimes  placed  upon  this  instrument  an  adjustable  wye 

with  a  micrometer  screw  arrangement  for  the  pointing  of  the  telescope  and  setting  of  the  bubble 
independently  of  the  leveling  screws.  The  very  marked  wear  on  the  collars  at  the  point  of 
contact  in  the  wyes  when  the  telescope  is  moved  in  altitude  has  induced  us  to  abandon  this  feature. 
A  perfect  instrument  in  this  line  and  at  the  same  time  entirely  free  from  any  change  in  height  when 
the  micrometer  screw  is  extensively  used  during  an  extended  leveling  operation  is  our  Engineers' 
Precise  Level,  page  139.  This  latter  instrument  is  capable  of  the  most  precise  work  and  is  offered 
at  a  price  so  very  low  that  it  should  be  included  in  the  instrument  equipment  for  precise  leveling 
of  any  magnitude. 

To  prevent  a  change  of  height,  after  an  appropriate  leveling  of  an  instrument  with  three 
leveling  screws,  it  is  advisable  to  clamp  one  of  the  leveling  screws  by  its  clamp  screw  at  the  side, 
and  to  level  up  by  the  other  two  screws  alone.  This  should  be  done  in  like  manner,  also,  to  correct 
for  slight  changes  in  the  level  caused  by  the  settling  of  the  tripod-legs. 

*  Four  leveling  screws  commend  themselves  in  the  more  ordinary  class  of  instruments  for 
the  greater  rapidity  with  which  an  instrument  can  be  leveled  up  approximately,  and  that  (no  mat- 
ter how  much  the  leveling  screws  may  be  worn)  when  brought  to  a  true  bearing  on  the  lower  level- 
ing plate,  all  such  looseness  is  taken  up. 

**NOTE:  In  some  types  of  leveling  instruments  numnted  on  a  three-screw  leveling  base  the 
latter  is  often  too  small  for  the  length,  power,  height  and  weight  of  the  instrument,  making  it  top 
heavy,  thereby  rendering  it  unsteady  and  unsuitable  for  close  work. 


137 
C.  L.  BEKGEB  &  SONS. 


3  » 

S3- 


Code  Word   Andromeda. 


138 

Reversion  Level. 

Applicable  to  any  of  our  Engineers'  Wye  Levels* 


The  spirit  level  used  in  this  feature  differs  from  the  ordinary  one  in  that  it  is 
ground  to  the  true  shape  of  a  barrel  so  that  the  tangents  to  the  level  bubble  curves,  at  the 
zero  points  of  the  scales,  are  parallel  and  diametrically  opposite.  By  the  use  ot :  this  rever- 
sion level,  attachable  to  any  of  our  Engineers'  Wye  Levels,  in  place  of  the  single  read- 
ing level,  it  is  possible  to  do  good  leveling,  though  the  adjustments  of  the  spirit  level 
and  cross  wires  are  entirely  deranged  and  the  collars  worn  (see  remark  below),  by  first 
making  the  level  bubble  central  and  taking  a  reading,  then  by  revolving  the  telescope 
180°  in  its  wyes,  which  point  is  indicated  by  an  adjustable  stop,*  making  the  bubble 
again  central  and  taking-  another  reading.  The  arithmetical  mean  is  the  correct  result. 

This  device  will,  in  an  emergency,  be  appreciated  when  it  is  known  that  by  the  use 
of  the  method  above  the  work  will  average  a^  good  as  that  done  with  an  ordinary  good 
wye  level,  in  adjustment.  The  adjustment  of  an  instrument  provided  with  a  reversion 
level  is  made  in  precisely  the  same  manner  as  if  the  spirit  level  was  of  the  single  read- 
ing kind,  since  the  adjustment  of  the  level  when  it  is  reversed  will  take  care  of  itself. 

The  reversion  level  is  guarded  by  a  revolvable  outnr  tube  (Patented,  not  shown  in 
cut)  leaving  a  space  of  air,  as  a  non-conductor  of  heat  between  it  and  the  ordinary  level 
mounting  tube.  This  exterior  tube  serves  both  as  a  protection  against  breakage  and 
sudden  changes  of  temperature,  and,  as  its  inner  surface  is  painted  white,  it  also  acts 
as  a  reflector  which  facilitates  the  reading  of  the  bubble. 

IJemark:  The  inequality  of  worn  collars  cannot  be  eliminated  in  a  strict  sense 
by  using  the  reversion  level,  yet  for  ordinary  good  work  it  may  be  said  to  be.  Nor  can 
the  test  for  the  equality  of  the  collars  be  directly  tested  in  this  way  but  should  be  done 
as  in  the  case  of  the  ordinary  wye  level ;  viz ,  by  the  two-peg  method  described  under 
the  adjustment  of  the  Dumpy  Level  (pages  63  and  64  of  our  handbook).  The  follow- 
ing modification  is  to  be  noted:  After  the  line  of  collimation  has  been  adjusted  for  dis- 
tant objects  by  rotating  the  telescope  in  its  wyes  and  the  spirit  level  has  been  adjusted 
by  reversing  end  for  end  and  adjusted  laterally,  (the  telescope  having  the  sunshade  at- 
tached, as  it  serves  to  balance  the  telescope  when  the  object  slide  is  drawn  in),  the  in- 
strument is  set  up  close  to  the  near  target,  and  a  reading  is  taken  with  the  level  tube 
in  the  direct  position.  In  order  to  eliminate  the  error  of  collimation  for  nearer  objects, 
should  any  exist,  another  reading  is  taken  with  the  telescope  rotated  180°  in  the  wyes, 
and  the  mean  taken  as  the  true  reading.  If,  now,  the  horizontal  wire  also  bisects  the 
distant  target  and  the  bubble  remains  central  in  each  position  of  the  telescope,  the 
collars  are  of  equal  diameter.  Should  the  latter  not  be  the  case,  the  error  may  be  cor- 
rected thus :  Bisect  the  distant  target  with  the  telescope  in  its  direct  position,  and  adjust 
the  level  till  the  bubble  is  central.  Rotate  the  telescope  180°  in  its  wyes,  indicated  by 
the  stop,  and  note  the  number  of  divisions  through  which  the  bubble  moves  in  order 
that  the  distant  target  remains  bisected,  so  that  a  correction  can  be  made  when  most 
precise  work  is  required. 

It  is  assumed  that  in  making  this  test  the  temperature  of  the  two  collars  has  been 
alike  and  that  the  telescope  has  been  in  proper  balance  by  being  focussed  for  a  distance 
of  about  300  feet  with  sunshade  attached.  A  scratch  on  the  telescope  or  object  slide 
indicates  the  focus  which  the  maker  used  in  equalizing  the  collars.  An  apparent  error 
found  as  above  may  be  due  to  a  change  in  the  shape  of  the  level  tube  which  may  occur 
in  time  (for  which  the  maker,  of  course,  cannot  be  held  responsible),  as  well  as  to  a 
worn  condition  of  collars,  or  these  causes  combined. 

In  order  to  trace  the  error  to  its  source  the  only  sure  test  is  made  with  a  striding 
level.  (See  Engineer's  Precise  Level.) 

Price,  as  above,  if  ordered  with  our  Wye  Level  in  place  of  the  single  reading 
kind  .'.../ $20.00. 

Y  It  is  an  extremely  difficult  matter  to  glint5  a  level  of  this  kind  so  that  the  bubble  will  remain  central  at 
all  positions  during  this  rotation  through  180°.  The  stop  just  mentioned  is  so  adjusted,  however,  by  the  maker, 
that  when  the  level  has  been  turned  exactly  180°  it  gives  a  correct  reading. 


139 

C  L.  BERGER  &  SONS'  ENGINEERS'  PRECISE  LEVEL. 

Patented.     {For  cut  see  page  141.} 

With  micrometer  screw  for  close  setting  the  spirit  level. 

For  use  in  cities  in  establishing  benches,  etc.,  also  for  all  work  requiring  speed  and  the  highest 
degree  of  accuracy  in  spirit  leveling. 

It  is  a  well-known  fact  that,  satisfactory  as  it  may  be  on  account  of  its  great  sim- 
plicity and  compactness,  the  ordinary  wye  level  (pp.  134,  135)  will  fail  in  degree  of  ac- 
curacy or  in  rapidity  of  manipulation  when  the  closest  results  are  required.  It  often 
happens  when  precise  work  is  required,  the  time  spent  in  leveling  up  and  keeping  the 
level  bubble  of  an  ordinary  good  wye  level  in  the  center  of  its  graduation  by  means  of 
the  four  leveling  screws  is  often  very  considerable  and,  when  the  course  is  over 
swampy  or  frozen  ground,  the  vexation  attending  the  work  is  apt  to  be  great,  and  the 
results  vitiated  by  the  numerous  readjustments  required  to  keep  the  bubble  in  its 
place.  This  manipulating  of  the  leveling  screws  is  very  apt  to  lead  to  a  change  in  the 
height  of  the  telescope,  varying  in  magnitude  according  to  the  style  of  the  instrument. 
(It  is  here  to  be  noted  that  this  change  in  the  height  of  the  telescope  is  less  in  our 
levels,  or  transits  with  leveling  attachments,  than  is  the  case  with  the  instruments 
of  other  makes). 

To  aid  the  Engineer  in  the  prosecution  of  exact  work,  avoiding  the  errors  caused 
by  the  readjustments  above  referred  to,  we  have  designed  and  are  prepared  to  furnish 
the  instrument  shown  on  page  141. 

By  referring  to  the  cuts  it  will  be  seen  that  this  instrument  is  mounted  on  three 
leveling  screws,  and  that  the  center  about  which  the  instrument  revolves  is  unusually 
long  and  unyielding.  Two  small  spirit  levels  attached  to  arms  extending  from  what 
we  may  call  the  cross-bar  (since  the  center  of  the  instrument  is  permanently  secured 
to  it  as  in  the  ordinary  style  of  levels)  serve  to  put  the  center  in  a  vertical  position, 
thus  securing  at  once  a  nearly  horizontal  position  to  the  cross-bar.  These  small  levels 
are  adjusted  the  same  as  the  ordinary  piaie  levels  of  a  transit. 

At  the  eye  end  this  cross-bar  carries  a  micrometer  screw  by  which  the  telescope 
and  its  level  can  be  raised  or  lowered  at  will  independently  of  the  leveling  screws.  A 
strong  spiral  spring  on  the  same  side  holds  the  wye-bar  down  upon  the  micrometer 
screw.  This  arrangement  provides  a  most  delicate  motion  up  and  down,  and  enables 
one  to  set  the  bubble  accurately  at  every  sight  and  in  a  very  much  better  manner  than 
can  be  done  by  the  leveling  screws  alone.  The  head  of  the  micrometer  screws  is  di- 
vided into  one  hundred  parts,  and  as  a  rule  its  pitch  will  be  such  that  250  to  252  parts 
of  revolution  of  the  screw  will  make  a  change  of  one  foot  in  the  reading  of  the  rod  held 
at  a  point  100  feet  away  from  the  center  of  the  instrument.  It  may  be  seen  that  the 
instrument  can  be  very  advantageously  used  for  making  grade  measurements.  The 
graduated  disc,  when  reading  zero  on  the  index-bar,  brings  the  instrument  at  once 
within  one  or  two  divisions  of  its  normal  position.  The  di-c  can  also  be  readily  turned 
on  its  hub  by  taking  hold  of  the  mille'l  head  (the  disc  is  held  on  its  arbor  simply  by 
friction),  so  that,  for  convenience,  a  reading  may  always  start  from  zero,  though  the 
cross-bar  be  not  leveled  up.  This  instrument,  as  above  stated,  is  provided  with  three 
leveling  screws,  which  give  a  firm  support  on  the  tripod,  and  allow  a  closer  setting  of 
the  bubble  when  the  instrument  is  run  as  an  ordinary  wye  level,  without  making  use 
of  the  micrometer.  (Seep.  44.) 

The  Chief  Feature  of  the  Instrument,  however,  consists  in  the  fact  that  the 
pivots  *  ou  which  the  wye  bar  can  be  raised  or  lowered,  are  in  the  middle  of  the  instru- 
ment and  within  a  fraction  of  an  inch  of  the  plane  of  the  line  of  collimation,  thus  se- 
curing to  the  telescope  a  motion  in  altitude  free  from  any  change  in  height  of  the  line 
of  collimation,  though  the  telescope  were  to  move  throughout  the  entire  range  of  the 
micrometer  screw  during  an  extended  leveling  operation.  As  9  rule,  the  working  range 
of  the  micrometer  will  be  limited  to  a  few  revolutions  each  way  from  its  normal  posi- 
tion in  order  to  keep  the  instrument  as  compact  as  possible.  The  instrument  is  also 
arranged  so  that,  whenever  desirable,  it  may  be  used  as  an  ordinary  wye  level.  For 
this  purpose,  it  is  provided,  at  the  object  end  of  the  cross-bar,  opposite  the  micrometer 
screw,  with  a  milled-head  screw  and  check  nut,  by  means  of  which,  and  by  the  micro- 
meter screw,  whep  set  at  zero  (see  cul),  the  wye  bar  may  be  set  exactly  at  right  angles 
to  the  vertical  center.  However,  for  the  fine  settings  of  the  bubble  in  bench  leveling 
or  pointing  of  the  telescope,  etc.,  the  micrometer  screw  should  be  used  exclusively. 

A  clamp  and  tangent  screw  motion  is  also  provided  and  so  arranged,  that  it  can 
be  readily  reached  from  the  eye  end  of  the  telescope.  The  cross  and  wye-bars  are 
cast  hollow  and  the  former  fits  inside  the  latter. 

*NOTE.— It  will  be  noticed  that  in  instruments  of  a  similar  character,  having  pivot  screws  acting  in  and  below 
the  wye  opposite  the  micrometer  screw,  as  for  instance,  in  the  TJ.  S  Coast  Survey  geoaesic  leveiSj  designed 
after  Stampfer  (see  Reoort  1879),  any  motion  ot  the  telescope  in  altitude  will  also  change  its  height.  By  an 
injudicious  use  of  the  micrometer  screw  our  own  hvdrographic  wye  level  (see  page  1043,  catalogues  1888-1891). 
partook  of  this  same  error,  and  this  together  with  the  marked  wear  on  the  collars  due  to  this  same  motion  led 
us  to  the  abandonment  of  it.  We  note,  however,  that  other  firms  who  are  in  the  habit  of  copyh^'our  style* 
aed  patterns  have  since  brought  it  out  as  a  detail  of  a  precise  level. 


140 

The  Telescope  will  be  invariably  inverting  in  order  to  admit  of  as  large  an  aperture  and  as  high  a  powei 
as  is  possible.  Thus  :  its  aperture  will  be  i  J£  inches,  the  total  length  is  about  17  inches,  and  it  will  have  a 
magnifying  power  of  40  diameters.  It  will  be  provided  with  fixed  stadia  wires,  in  the  proportion  of  i  to  100, 
the  distance  to  be  measured  Irom  a  point  in  front  of  the  objective  equal  to  its  focal  length 

The  Spirit  Level  is  of  the  single  reading  kind,  and  is  generally  made  so  that  one  division  (of  -rV  of  an 
inch)  equals  from  8  to  10  seconds  of  arc.  The  sensitiveness  of  the  level  will,  however,  be  adapted  to  the  par- 
ticular requirements.  It  is  not  necessary,  however,  to  have  it  any  more  sensitive  than  is  required  for  a  fine 
field  instrument,  as  an  over-sensitive  level  is  apt  to  give  more  trouble  than  benefit  in  its  use. 

A  Reversion  Level  of  same  sensitiveness  might  be  applied  instead  of  the  single  reading  level,  if  desired, 
as  a  convenience  (see  Reversion  Level  p.  136),  when  the  highest  precision  is  not  needed.  Of  course  in  fine  work 
the  reversion  level  must  be  used  in  the  direct  position  as  with  a  single  reading  level.  However,  one  will  un- 
derstand that  a  reversion  level  is  very  apt  to  change  its  true  barrel  form  in  time  thus  becoming  wholly 
unreliable,  and  therefore  we  do  not  advise  it  at  all,  and  particularly  not  for  an  instrument  of  such  a  fine 
character  as  this  is. 

A  Metal  Mirror  will  be  furnished  with  the  instrument,  attachable  to  either  side  of  the  level,  enabling  the 
operator  to  read  the  bubble  without  stepping  aside  ;  a  convenience  which  will  be  appreciated  when  working  on 
shaky  ground. 

Adjustment.  The  adjustment  of  the  telescope  and  the  level  must  be  made  precisely  as  in  an  ordinary 
wye  level.  (See  adjustment  of  the  wye  level,  pages  59  and  63  of  this  hand-book  )  The  spirit  level  will  be  in 
thorough  adjustment  when  the  telescope  with  its  sunshade  attached  is  focussedfor  a  distance  of  about  400  feet, 
when  the  telescope  is  in  perfect  balance  and  the  equality  of  the  collars  is  assured  thereby  ;  for  shorter  distances, 
however,  there  is  a  small  error  due  to  the  unbalancing  of  the  telescope  caused  by  the  object  slide  being  thrown 
out.  Small  as  this  error  may  be  it  can  be  entirely  eliminated  by  simply  bringing  the  bubble  to  the  center  by 
the  use  of  the  micrometer  screw. 

Explanation.  The  foregoing  has  been  written  at  some  length  to  give  a  clear  understanding  of  the  prin- 
cipal features  of  this  instrument.  Naturally,  the  question  may  now  present  itself,  why  not  use  a  striding  level 
alone,  in  place  of  the  fixed  or  reversion  level,  as  is  done  in  some  of  the  best  types  of  instruments,  particularly 
as  the  pivot  arms,  extending  from  the  middle  of  the  cross-bars,  must  necessarily  be  spread  quite  a  distance 
apart,  to  readily  permit  the  revolution  of  the  telescope  with  the  fixed  level  in  the  wyes.  To  this  we  may  say, 
that  a  fixed  level  placed  below  the  telescope,  where  it  is  guarded  against  breakage  and,  in  a  measure,  from  the 
action  of  the  sun,  is  better  adapted  to  the  wants  of  the  Civil  Engineer  in  running  quick  and  accurate  levels 
in  cities,  towns,  etc.,  than  a  striding  level  with  its  more  cumbersome  features  and  manipulations  would  be, 
particularly  if  the  work  was  to  be  of  the  most  precise  character. 

It  is  only  when  the  collars  of  a  telescope  are  badly  worn  or  imperfectly  made  that  the  striding  level  has 
any  advantage  over  a  fixed  one.  As  a  rule  a  fixed  level  keeps  in  better  adjustment,  is  simpler  to  manipulate 
than  the  striding  level,  and  is  free  from  the  errors  due  to  the  uncertainty  of  contact  of  the  collars  and  the  wyes. 
Moreover,  the  construction  of  the  new  instrument  is  such  that  it  has  a  greater  stability  than  those  of  previous 
make.  We  therefore  believe  that  the  fixed  level  has  as  legitimate  a  standing  as  the  striding  one. 

For  the  above  and  similar  reasons  the  American  Engineers  have  and  will  give  preference  to  the  instru« 
ment  which  has  the  level  fixed  to  the  telescope;  and  this  has  led  us  to  the  adoption  of  this  feature  in  our  new 
instruments.  This  idea  is  also  prevalent  among  the  best  instrument  makers  and  engineers  in  Europe,  as  may 
be  seen  by  examining  Prof.  Nagel's  published  description  of  a  similar  instrument. 

Instrument,  Finish,  Packing*,  Weight,  etc.  The  telescope  is  leather-finish, 
while  some  of  the  more  bulky  parts  of  the  instrument  are  simply  treated  either  with 
cloth  finish  or  japan,  in  order  to  lessen  the  cost  No  attempt  will  be  made  to  give  an 
elaborate  finish  at  the  expense  of  accuracy  and  utility ;  altogether,  as  all  the  other 
parts  will  be  bronzed  and  lacquered  in  a  manner  customary  with  us,  it  will  present  a 
handsome  appearance.  This  instrument  is  packed  erect  in  one  box  in  the  same  man- 
ner as  we  pack  the  regular  engineer's  wye  level.  It  is  secured  to  the  tripod  in  the 
same  manner  as  are  all  of  our  instruments  with  three  leveling  screws.  (See  page  136 
for  description  ) 

The  mahogany  box  contains  a  sunshade,  wrench,  screw-driver  and  adjusting  pin. 

Weight  of  instrument,  !!-£  pounds;  weight  of  tripod,  10-J  pounds;  weight  of  ma- 
hogany box,  10|  pounds  ;  gross  weight  of  instrument  complete,  securely  packed  in  two 
boxes  for  shipment,  60  Ibs. 
Price  of  this  instrument,  inverting  telescope,  leather-finish,  fine 

mirror  mounted  in  case,  fixed  stadia  wires,  and  a  single  reading  fixed 

spirit-level, ...     $215.OO 

Extras  to  Engineers'  Precise  Level 

Center  of  instrument  made  of  steel,  and  hardened  and  running  in  a  socket  of 

cast  iron,  improved  style  (see  cut,  page  135),  ....  15.00 

Sunshade  with  smaller  aperture,  for  use  with  the  telescope  when  the  sun 

rays  are  too  bright  for  accurate  work, 1.00 

Gossamer  bag,  to  protect  instrument.        ....                ...  1.00 

Bottle  of  fine  watch  oil  for  lubricating  the  centers,  etc., 0.35 


t  If  geodesic  work  is  to  be  done, 


,  higher  sensibility  might  be   permissable,  but  our  customary  fluid  would  be  sluggish  in 
ave  to  be  filler!  with  pure  ether,  in  order  to  make  it  quick  acting  (see  pages  7,    *8,  38). 


, 

An  air  chamber  would  be  necessary  to  allow  for  adjustment  of  the  bubble,  which  in    this  case  changes  its  length  rapidly  for 
perature.     By  adding  a  chamber,  a  feature  is  introduced  which  is  liable  to  affect  the  reliability  of  th« 


sltehr  changes  in  temperature.     By  adding 
Spirit  level  and  entail  extra  expense 


Code  Word.     Engineers'  Precise  Lev«i  bnt  witn  steel  centre    Arethusa 


141 


H 

3 
M 


142 

THE  GEODETIC  LEVEL. 

In  response  to  a  request  of  President  T.  C.  Mendenhall  to  construct  i«r  the 
Worcester  Polytechnic  Institute  a  Precise  Wye  Level,  the  senior  member  of  this  firm 
in  1896  designed  and  made  the  type  shown  on  next  page. 

The  leading  features  are  great  compactness,  rigidity,  simplicity  of  design,  ease  of 
manipulation,  and  thorough  adaptation  of  every  part  to  its  purpose.  In  order  to  lessen 
the  height  above  the  tripod,  the  weight  of  the  instrument  and  the  surfaces  exposed  to 
wind  pressure,  this  particular  form  of  cradle  bar  has  been  adopted  ;  and,  while  this 
reduction  might  have  been  carried  to  a  greater  extent  by  placing  tae  vertical  revolving 
center  inside  the  tripod  head,  it  was  thought  not  advisable,  as  sometimes  it  is  desirable 
to  set  the  instrument  on  the  leveling  screws  when  detached  from  the  tripod. 

As  will  be  seen,  the  improved  tripod  is  of  a  very  stiff  form,  which  is  necessary 
where  telescopes  of  great  power  and  highly  sensitive  spirit  levels  are  used.  To  eliminate 
the  effect  of  unequal  expansion,  the  telescope  collars  are  of  smallest  possible  diameter 
compatible  with  the  diameter  of  the  object  glass,  and  at  first  were  of  hardened  steel 
resting  on  agates  at  point  of  contact  in  wyes.  The  striding  level  adopted  in  place  of 
the  fixed  level  is  of  tubular  form  and  has  very  short  legs.  To  still  further  reduce  the 
effect  of  unequal  expansion,  the  substructure,  such  as  cradle  bar,  fixed  bar  and  other 
parts,  below  the  agates  at  point  of  contact  in  wyes  in  this  instrument,  consisted  of  steel 
and  iron.  Subsequently,  however,  as  the  danger  of  rusting  in  the  field  became  very 
apparent,  the  use  of  steel  and  iron  was  not  thought  to  be  as  important  in  portable  field 
instruments  when  used  on  tripods  as  in  the  stationary  astronomical  instruments :  there- 
fore we  are  making  the  substructure  of  our  customary  hard  gun-metal,  and  shall  so 
furnish  them,  unless  ordered  to  be  of  steel,  in  which  ca.se  the  instrument  will  have  to 
be  specially  made.  (See  below.)  The  same  may  be  said  of  the  hardened  steel  collars. 
Unless  ordered  otherwise  the  collars  will  be  made  of  hardest  bell-metal. 

All  the  parts  that  must  be  handled  during  a  field  operation  are  protected  by  a 
shield  of  a  non-heat-conducting  material.  By  means  of  a  micrometer  screw  the  telescope 
can  be  moved  in  the  vertical  plane  around  the  center  in  the  middle  of  the  instrument 
in  order  not  to  disturb  the  height  of  the  intrament. 

The  striding  level  has  a  bubble  tube  reading  to  3''  of  arc  and  is  provided  with  an 
air  chamber.  Mounted  above  it  is  a  mirror  to  enable  the  observer  to  read  the  bubble 
without  stepping  aside.  Provision  is  made  to  readily  lock  the  striding  level  to  the 
cradle  bar,  to  enable  one  to  use  the  instrument  like  an  ordinary  Wye  Level  (with  level 
fixed  to  the  telescope) ;  and  to  carry  the  instrument  on  its  tripod  from  station  to  station. 
An  arrangement  is  also  provided  by  which  the  striding  level  upon  reversing  will  always 
find  its  proper  plane  on  the  collars,  so  as  to  require  but  very  little  attention  on  the  part 
of  the  operator.  By  means  of  a  clamp  screw  opposite  the  micrometer  screw  the  cradle 
bar  can  be  secured  so  that  the  instruments  can  be  used  for  ordinary  wye  level  work. 

Two  auxiliary  levels  placed  at  right  angles  serve  to  level  up  approximately  ;  after 
which  the  final  setting  of  the  striding  level  is  done  by  the  micrometer  screw  attached 
to  the  fixed  bar.  The  vertical  center  is  of  hardened  steel  and  runs  in  a  socket  of  cast 
iron.  All  the  main  parts  are  either  cloth  finished  or  japanned.  The  beautiful  appear- 
ance of  the  instrument  does  not  depend  upon  the  external  finishing  and  polishing  of 
parts,  but  entirely  upon  the  harmony,  simplicity  and  excellence  with  which  the  essential 
features  of  the  instrument  are  designed. 

For  a  detailed  description  of  the  instrument  we  refer  to  a  paper  read  by  Mr.  David 
Molitor  before  the  Am.  Soc.  of  C.  E.  (See  Proceedings  1899-1900.) 

The  telescope  is  inverting,  with  an  object  glass  of  1^"?  focal  length  of  17", 
and  a  power  of  40  diameters.  It  is  provided  with  the  usual  cross  and  stadia  wires. 
Instrument  packs  in  pine  wood  box,  which  contains  a  sunshade,  screw  driver,  adjusting 
pin  and  gossamer  bag. 

Weight  of  instrument         .......  14  Ibs. 

Weight  of  tripod  15  Ibs. 

Gross  weight  of  instrument  packed  securely  for  shipment  in  two  boxes    75  Ibs. 

Price  as  above,  of  brass  and  bell  metal  collars,          .        .        ...     $280.00 
Price  of  instrument,  substructure  of  steel,  as  above,  extra,    .         .  25.00 

Price  of  instrument,  collars  of  telescope  of  hardened  steel,  extra,      .          25.00 


Code  Word  for  Geodetic  L,ev«i  of  brass  and  bell  metal  collars  Artemisia 


143 


The  Berger  Geodetic  Level. 


144 

COAST  SURVEY  PRECISE  LEVEL 

The  demand  for  a  level  whereby  the  utmost  precision  possible  in  leveling  may  be  ob- 
tained comes  from  many  sources  in  work  where  the  absolutely  correct  determination 
of  the  relative  height  of  a  line  of  benches  is  sought. 

The  Coast  Survey  Precise  Level,  illustrated  by  accompanying  cuts,  is  designed  to 
meet  this  demand ;  and  it  is  probably  the  most  perfect  instrument  made  of  the  dumpy 
level  type. 

The  essential  feature  which  gives  value  to  this  instrument  is  the  fixed  adjustment  be- 
tween the  line  of  collimation  and  the  level  by  the  use  of  nickel  iron,  with  coefficient  of 
expansion  of  0.000004  per  degree  Centigrade,  in  combination  with  nickel  steel,  with 
coefficient  of  expansion  of  0.000001  per  degree  Centigrade ;  and  the  location  of  the  level 
partially  within  the  telescope  and  as  near  as  possible  to  the  line  of  collimation. 

The  instrument  is  so  made  that  the  line  of  collimation  is  adjusted  by  the  maker  once 
and  for  all  as  in  our  Dumpy  Level,  by  revolving  the  telescope  in  auxiliary  wyes  on 
rings  turned  concentric  with  the  bore  of  the  telescope  tube.  If  it  becomes  necessary 
to  replace  broken  wires  in  the  field,  the  reticule  must  be  removed,  wires  and  reticule 
then  replaced  in  the  telescope,  and  adjusted  for  collimation  by  its  capstan-headed 
screws  and  the  two-peg  method.  This  latter  operation  assumes  that  the  position  of 
the  spirit  level  in  relation  to  the  telescope  has  not  been  disturbed,  and  that  its  adjust- 
ment is  still  perfect  or  nearly  so. 

An  important  feature  of  the  instrument  is  the  prismatic  reading  attachment  for  the 
level  bubble,  whereby  the  observer  reads  with  one  eye  the  rod  and  with  the  other  eye 
the  level  simultaneously  without  change  of  position. 

With  short  sights  the  instrument  permits  great  accuracy  and  quick  action  in  skilled 
hands. 

Standing  erect,  the  observer  takes  the  back  sight  by  reading  the  three  horizontal 
wires  on  the  "self-reading"  rod,  and  then  again  the  middle  wire  as  a  check,  each  of  the 
readings  being  made  with  the  bubble  set  to  the  normal  by  means  of  the  vertical  fine 
motion  screw.  Swinging  the  telescope  round  to  the  forward  rod,  he  repeats  this  pro- 
cess for  the  foresight .  The  records  of  the  Coast  and  Geodetic  Survey  show  that  the  time 
of  occupying  one  station  is  somewhat  less  than  5  minutes.  In  the  season  of  1911  one 
of  the  engineers  of  the  Survey  ran  14.35  miles  single  or  11.547  kilometers  completed 
(back  and  forth)  line  in  one  day  of  7  hours  30  minutes  actual  work.  None  of  this  level- 
ing required  re-running,  all  of  it  closing  within  the  error  of  tolerance,  i.  e.,  4  mm  -v/K~ 
in  which  K  stands  for  the  distance  expressed  in  kilometers. 

In  constructing  this  instrument  we  follow  absolutely  the  Coast  Survey  specifica- 
tions, using  nickel-iron  and  nickel-steel  as  called  for,  thus  insuring  a  rigid  maintenance 
of  the  adjustment  of  instrument  under  marked  changes  of  temperature. 

This  level  is  guaranteed  to  pass  the  Coast  Survey's  inspection. 

For  details  of  construction  and  use,  see  Transactions  of  the  American  Society  of 
Civil  Engineers,  June,  1901,  pp.  127-175 ;  U.  S.  Coast  and  Geodetic  Survey  Report  for 
1902,  Appendix  No.  4,  and  Report  for  1900,  Appendix  No.  6. 

SPECIFICATIONS :  — 

Telescope,  inverting,  length  17  inches,  aperture  1^",  power  about 

40  diameters. 
Level  to  telescope,  length  53^  inches,  chambered,  graduated  in  2  mm 

divisions — each  sensitive  to  2"  of  arc. 
Stadia  wires,  ratio  30  cm  to  100  meters. 
Micrometer  screw,  100  revolutions  to  1  inch;  head  divided  into  100  parts. 

A  cam  is  provided  for  lifting  telescope  from  micrometer  screw 

when  not  in  use. 

Weight  of  tripod,  about  19  Ibs. ;  in  packing  box  about  50  Ibs. 
Weight  of  instrument,  about  14  Ibs. ;  in  instrument  box  about  30  Ibs. 
Gross  weight  of  level  packed  securely  in  two  boxes  for  shipment,  about 
120  Ibs. 

Code  word,  Aster.  Price  $375.OO 


145 
C.  L,.  BEBGEK  &  SONS. 


o 

o 


I 


146 

PLANE  TABLE 

This  instrument,  as  shown  in  cut  on  opposite  page,  has  been  designed  to  fill  a  want 

where  a  high  class  of  work  in  topography  is  required.      It  IS  made  1U  two  sizes.      The 

alidade  is  built  strong  and  light.  The  ruler  is  of  brass.  Other  parts  are  of  alumi- 
num, or  brass,  as  best  serving  the  purpose.  The  telescope  is  well  lighted,  powerful, 
and  of  greater  length  than  usual,  the  latter  enabling  the  observer  to  readily  sight 
at  an  object  when  the  alidade  is  some  distance  from  the  edge  of  the  board.  The  ruler 
is  provided  with  two  fixed  levels  and  is  so  arranged  that  lines  can  be  ruled  in  the 
vertical  plane  of  the  telescope,  if  desired. 

To  obtain  great  rigidity  and  strength,  the  diameter  of  the  bearing  surface  of  the  lower 
motion  in  both  sizes  is  larger  than  usual  and  the  board  rests  on  radial  arms  extending 
considerably  beyond  this  bearing  surface.  The  tripod  head  is  of  corresponding  size. 
To  be  portable,  all  the  essential  parts  are  built  on  the  skeleton  plan.  To  avoid  a  loosen- 
ingof  the  leveling  screw  fastenings  so  often  experienced  where  the  latter  are  fitted 
into  tripod  heads  made  of  wood,  we  make  this  head  of  composition  brass,  or  of  alu- 
minum, and  to  prevent  all  wabbling  of  the  leveling  screws  when  worn,  these  latter  are 
also  provided  with  check  nuts.  Materials  and  workmanship  are  of  the  best. 

SPECIFICATIONS:  — 
Alidade.  Length  of  ruler  22  inches. 

Telescope.  Inverting.  Aperture  l^g  inches.  Length  16  inches.  Power  35  dia. 

(For  adjusting  the  line  of  collimation,  the  .telescope  can  be  revolved 
180°  on  its  longitudinal  axis. 

Stadia  wires.  Katio  1 : 100. 

Vertical  arc.  4}^  inches,  graduated  on  solid  silver,  double  verniers  reading  to 

minutes.  —  The   vernier  arm  is  provided  with  a  level  on  top  for  a 
ready  control  of  zero  of  verniers. 

Striding"  level.  6  inches  over  all. 
Compass  needle.  4^  inches. 
Lower  motion,  (usual  size)  with  tangent  screw  (for  boards  24  X  30  in.  or  22  X 

24  in.)     Spread  of  arms  from  center  4^  inches. 

Weight  of  Alidade  with  brass  ruler,  ....          about        7  Ibs. 


"        "  Lower  motion,  usual  size,  with  arms  4^  inches, 

"        "  Tripod, 

"       "  Board, 

6f      "  Alidade  and  accessories  in  mahogany  box, 
"        "  Lower  motion  in  special  box,  with  legs  detached, 
«  Board  in  canvas  case, 


-9 

15* 
9 

18 
15 
11 


Gross  weight  of  instrument  packed  in  four  boxes  ready  for  shipment,  100 

Price  of  Plane  Table  as  above,  and  as  in  cut,  including  one  board 
24  X  30  inches,  detached  compass,  screw-driver,  clamps,  reading 
glass,  plumb-bob,  (board  and  tripod  packed  in  pine  wood  ship- 
ping cases,  alidade  with  attachments  in  mahogany  box,  lower 
motion  in  pine  wood  box)  ........  $3OO.OO 

Price  of  Alidade  alone,  as  above,  with  striding  level,  detach- 
able compass,  etc. ,  in  mahogany  box,  but  without  board  and  lower 
motion  and  tripod, $2OO.OO 

Price  of  Interchangeable  Micrometer 

Code  Word  — AtluS.  Made  to  order  only.     $5O.OO 

Price  of  Canvas  Case  for  board        .        .        .        .        .        •          $2.OO 

Note  :  Lower  motion  as  above,  but  with  a  bearing  surface  8  inches  in  diameter, 
having  arms  extending  to  6  in.  from  the  center,  can  be  supplied  for  regular  or  larger 
boards,  in  place  of  the  one  specified  above.  Weight  about  11  Ibs. 

Price  extra,  $1O.OO 

To  meet  a  want  where  greater  portability  and  lightness  are  thought  to  be  more  ad- 
vantageous than  greater  rigidity  and  consequent  accuracy,  we  are  prepared  to  furnish 
in  place  of  the  above  described  lower  motion  of  the  Plane  Table  (shown  in  the  accom- 
panying cut)  one  of  the  Johnson  type  and  character.  A  description  of  this  may  be 
omitted  here,  since  it  is  described  in  any  of  the  modern  text-books  on  Plane  Table 
Work.  Suffice  it  to  say  that  this  motion  is  operated  in  a  manner  similar  to  that  de- 
scribed under  our  Quick  Leveling  Attachment  (see  pages 45  and  118)  of  which  it  is  an 
inverted  adaptation,  but  is  of  greater  size,  range  and  steadiness. 

This  movement,  with  legs  all  complete,  weighs  only  from  9  to  10  Ibs. 

Price  of  Johnson's  Improved  Plane  Table  Movement, 

mounted  on  large  tripod     ......... 


147 

C.  L.  BEKGEK  &  SONS. 


61" 


150 

ENGINEERS'  AND  SURVEYORS'  TRANSIT. 


This  instrument  is  designed  for  engineering  work  of  a  high  class,  such  as  is  required 
in  bridge  building,  water-works,  and  for  city  and  land  surveying.  The  size  of  the  cir- 
cle is  such  that  it  may  be  graduated  to  read  to  30"  or  20"  without  fatigue  to  the  eye. 
The  telescope  is  of  the  best  definition,  and  has  a  large  aperture  with  perfectly  flat  lield. 
The  eye-piece  is  achromatic,  and  gives  a  large  field  with  plenty  of  light.  We  advise 
our  customers  to  order  solid  silver  graduations  for  this  instrument.  Silvered  gradua- 
tions are  made  to  order  only,  being  of  rare  inquiry. 

Transits  size  No.  1 — No.  Ic. 

Specifications  :  —  Horizontal  Circle 

614  in.  (edge  of  graduation),  double  opposite  verniers  read  to  minutes,  two  rows  of 
figures  in  opposite  directions  from  0°  to  360°,  figures  on  limb  and  verniers  inclined  in  the 
direction  they  should  be  read,  verniers  protected  with  fine  plate  glass,  and  provided  with 
glass  shades,  graduations  silvered;  long  compound  centers  with  heavy  flanges; 
edge-bar*  magnetic  needle  4'^  in.;  spring  tangent  screws;  fine  telescope 
11 1^  inches  long,  objects  erect,  aperture  1%  inches,  power  of  telescope  24  diani.  (well 
adapted  for  stadia  work),  eye  piece  provided  with  an  improved  screw  arrangement  for 
accurately  focussing  the  cross-wires,  telescope  perfectly  balanced  reverses  at  both  ends, 
line  of  collimation  correct  for  all  distances,  protection  to  object-slide,  adjustment  for  ver- 
tical plane  of  telescope ;  spirit  levels  of  standard  length,  ground  and  extra  sensitive ; 
shifting  center  to  set  the  instrument  exactly  over  or  under  a  given  point ;  top  of  telescope 
provided  with  a  very  fine  punch  mark  to  also  enable  to  center  the  transit  from  a  point 
above;  standards  leatherized  (see  p.  11),  full  length  split-leg  tripod,  etc. 

The  Mahogany  Case  has  a  leather  strap,  hooks,  etc.,  and  contains  a  sun-shade,  a 
wrench,  a  screw-driver,  an  adjustable  plumb-bob,  a  magnifying  glass,  adjusting  pin,  and 
weighs  from  9^  to  10  Ibs. 

Weight  of  Plain  Transit  No.  1 13%  Ibs. 

"  Transit  with  Level  Attachment  (No.  la)       14      " 
"  Complete  Transit  (No.  Ib  and  No.  Ic)    .        14%  " 

Gross  Weight  of  Instrument  complete,  packed  securely  for  shipment  in  two  boxes, 
about  60  Ibs. 

Plain  Transit,  size  No.  1,  as  described  above,  see  cut  on  opposite  page. 
Code  Word,  Babelle.  Price  (graduations  silvered),  $18O.OO 

Transit  NV).  la,  size,  etc.,  asunder  No.  1  above,  with  long,  sensitive  lev  el,  clamp 
and  tangent  screw  to  telescope,  see  cut  page  152. 
Code  Word,  Balnode.  Price  (graduations  silvered),  $21O.OO 

Transit  No.  1 1>,  size,  etc.,  as  under  No.  1  above,  but  with  a  level,  clamp  and  5-inch 
vertical  arc  to  telescope.  Arc  has  double  verniers  reading  to  minutes,  see  cut  page  153. 
Code  Word,  Besica.  Price  (graduations  silvered),  $225.OO 

Transit  No.  Ic,  size,  etc.,  as  under  No.  1  above,  but  with  a  level,  clamp  and 
5-inch  full  vertical  circle  to  telescope.     Vertical  circle  has  double  verniers  reading  to 
minutes,  and  is  protected  by  an  aluminum  guard,  as  in  cut  page  154. 
Code  Word,  Boscardo.  Price  (graduations  silvered),  $237«OO 


Extras  to  Plain  Transit  No,  1— Transit  No.  Ic  inclusive. 

Standards  polished  and  lacquered  (no  leather  finish),  made  to  order  only      .  $5.00 

Graduation  of  horizontal  circle,  on  heavy  inlaid  ring  of  solid  silver       .         .  10.00 

"      reading  to  30"          ...                  .  10.00 

"         "             "          »          "  20" 20.00 

"  vertical  arc  or  vertical  circle  on  heavy  inlaid  ring  of  solid  silver  5.00 

Gradienter  attachment  (see  pp.  6  and  45)          •         .         .      '  .         .         .         .  5.00 

Stadia  Wires,  fixed          .         .         .      "  .         .         .         .         .         .         .         .  3.00 

Short  Focus  Lens  (pp.  101,  203).     One  pair   .......  16.00 

Arrangement  for  offsetting  at  right  angles       .         .         .         .                 .         .  5.00 

Variation  plate,  adapted  for  ah  declinations  E.  or  W.    .         .         .         .         .  10.00 

Cravenette  hood  (heavy,  gives  good  protection);  Silk  (light,  not  waterproof)  each  1.00 

Bottle  of  fine  watch-oil  to  lubricate  the  centers,  etc.,  of  transit      .         .         .  0.35 

An  Inverting1  TeleSCOpe  of  iy&"  aperture,  \\%"  focal  length  and  power  of  28 
<lia.  can  be  supplied  with  the  above  transits  in  place  of  the  regular  erecting  one  at  110  additional 
cost.  This  telescope  is  particularly  well  adapted  for  stadia  work.  The  weight  is  9  oz.  more.  This 
instrument  is  made  to  order  only. 

*  Correct  form  having  no  index  error.     See  pages  98,  99. 


151 

C.  L.  BERGKR  &  SONS. 


K 


No.  1. 

in.  at  edge  of  graduation.) 


Plain  Transit. 


For  size  and  description  of  this  instrument,  as  well  as  for  Extras,  see  opposite  page. 

Plain  Transit  No.  1,  as  shown  above,  and  as  described  under  Plain  Transit  No.  1  (Babelle),  on 
opposite  page,  verniers  reading  to  minutes,  but  with  graduations  on  solid  silver,  as  usually  supplied. 

Code  word,  Babiana.  Price,     $19O.OO 

(For  code  words  for  Extras  and  changes  from  Babiana,  see  page  C  of  complete  code  at  back.) 
The  verniers  of  this  instrument  can  be  placed  at  an  angle  of  90°  to  line  of  sight,  if  so  ordered  to  be 
made  specially. 

Sketch  "A"  shows  the  bearings  in  the  standards  for  the  V-shaped  form  of  the  tele- 
scope's axis,  the  improved  manner  of  fitting  the  adjustable  "Wye  block  in  the  standard 
by  means  of  dovetails  instead  of  pins,  also  the  adjustment  of  the  block  by  opposing  cap- 
stan-headed nuts,  securing  thereby :  — 

1.  Greater  rigidity  of  the  bearing  block  in  the  standard,  resulting  in  a  truer  motion  of  the 
telescope. 

2.  Greater  ease  of  making  the  vertical  plane  adjustment,  as  compared  with  other  makes  of  the 
same  class. 

3.  Greater  permanency  of  this  adjustment  when  made. 


152 
C.  L,.  BERGER  &  SONS 


No.  1  a. 

614  in.  at  edge  of  graduation. 


Transit  with  Level  Attachment*  to  Telescope. 

For  size  and  particulars  of  this  instrument,  as  well  as  for  Extras,  see  page  ISO. 

Transit  No.  1  a,  same  as  shown  above,  and  as  described  under  Transit  No.  1  a. 
(Balnode),  page  150,  verniers  reading  to  minutes,  but  with  graduations  on  solid 
silver  and  with  fixed  stadia  wires  as  usually  supplied. 


Code  Word,  Balsam. 

(For  code  words  for  Extras  and  changes  from  Balsam, 
see  page  C  of  complete  code  at  back.) 


Price,  $223.OO 


The  verniers  of  this  instrument  can  be  placed  at  an  angle  of  90°  to  line  of  sight,  if  so 
ordered  to  be  made  specially. 

*  With  a  level  attachment  of  the  above  kind,  good  leveling  can  be  done,  as  the  power  of  the  telescope  and 
the  sensitiveness  of  the  spirit-level  are  equal  to  that  of  most  Wye-levels. 


153 
C.  L,.  KERGER  &  SONS 


No.  1  b. 

in.  at  edge  of  graduation.) 


Complete  Engineers'  and  Surveyors'  Transit. 

For  size  and  description  of  this  instrument,  as  well  as  for  Extras,  see  page  15O. 

Transit  No.  1  b,  as  shown  above,  and  as  described  under  Transit  No.  1  b  (Besica), 
on  page  150,  verniers  reading  to  minutes,  but  with  graduations  on  solid  silver  and 
with  fixed  stadia  wires  as  usually  supplied. 


Code  word,  Betonica. 

(For  code  words  for  Extras  and  changes  from  IJetonica, 
see  pages  C,  D  and  F  of  complete  code  at  back.) 


Price,  $243.OO 


The  verniers  of  this  instrument  can  be  placed  at  an  angle  of  90°  to  line  of  sight,  if  so 
ordered  to  be  made  specially. 


152 
C.  L,.  BERGER  &  SONS 


No.  I  a. 

T4  in.  at  edge  of  graduation.) 


Transit  with  Level  Attachment*  to  Telescope. 

For  size  and  particulars  of  this  instrument,  as  well  as  for  Extras,  see  page  ISO. 

Transit  No.  1  a,  same  as  shown  above,  and  as  described  under  Transit  No.  1  a. 
(Balnode),  page  150,  verniers  reading  to  minutes,  but  with  graduations  on  solid 
silver  and  with  fixed  stadia  wires  as  usually  supplied. 

Code  Word,  Balsam.  Price,  $223.OO 

(For  code  words  for  Extras  and  changes  from  Balsam, 
see  page  C  of  complete  code  at  back.) 


The  verniers  of  this  instrument  can  be  placed  at  an  angle  of  90°  to  line  of  sight,  if  so 
ordered  to  be  made  specially. 

*  With  a  level  attachment  of  the  above  kind,  good  leveling  can  be  done,  as  the  power  of  the  telescope  and 
the  sensitiveness  of  the  spirit-level  are  equal  to  that  of  most  Wye-levels. 


153 
C.  L.  BERGER  &  SONS 


.  1  b. 

In.  at  edge  of  graduation.) 


Complete  Engineers'  and  Surveyors'  Transit. 

For  size  and  description  of  this  instrument,  as  well  as  for  Extras,  see  page  ISO. 

Transit  No.  1  b,  as  shown  above,  and  as  described  under  Transit  No.  1  b  (Besica), 
on  page  150,  verniers  reading  to  minutes,  but  with  graduations  on  solid  silver  and 
with  fixed  stadia  wires  as  usually  supplied. 

Code  word,  Betonica. 


Price,  $243.OO 


(For  code  words  for  Extras  and  changes  from  lietonica, 
see  pages  C,  D  and  F  of  complete  code  at  back.) 


The  verniers  of  this  instrument  can  be  placed  at  an  angle  of  90°  to  line  of  sight,  if  so 
ordered  to  be  made  specially. 


154 
C.  L.  BERGER  &  SO>S 


No.  1  c. 

in.  at  edge  of  graduation.) 


Patented. 


Complete  Engineers'  and  Surveyors'  Transit. 

For  size  and  particulars  of  this  instrument,  as  well  as  for  Extras,  see  page  15O. 

Transit  No.  1  c,  same  as  shown  above,  and  as  described  under  Transit  No.  1  c. 
(Boscardo),  page  150,  verniers  reading  to  minutes,  but  with  graduations  on  solid 
silver- and  with  fixed  stadia  wires,  as  usually  supplied. 

Code  word,  Bouvarclia.  Price,  $255.OO 

(For  code  words  for  Extras  and  changes  from  Bouvardia, 
see  pages  C,  D  and  F  of  complete  code  at  back.) 


The  verniers  of  this  instrument  can  be  placed  at  an  angle  of  90°  to  line  of  sight,  if  so 
ordered  to  be  made  specially. 


155 


Special  Vertical  Circle. 

A  5  J-Inch  Vertical  Arc   or  Full  Circle  with   Hal    graduations  of  style 

shown  for  No.  1  b  and  No.  1  c  but  reading  to  3O"  can  be  furnished  in  place  of  the 
regular  5-inch.      Made  to  order  only. 


Code  Word  —  Bowaiia 


Price,  extra  $5.O<> 


Beaman  Stadia  Arc. 

An  attachment  for  reducing  inclined  stadia  readings  to  horizontal  distances,  and  at 
the  same  time,  giving  differences  of  elevation  between  instrument  and  base  of  rod.  It 
can  be  attached  to  Transits  with  flat  vertical  circles  5|,  5  and  4  inches  diameter  and 
having  the  verniers  between  the  legs  of  standards,  as  in  ]Vo.  1  c. 

It  may  also  be  used  for  arcs  with  an  open  edge  graduation,  as  for  Plane  Table 
Alidades,  etc.     Attached  to  our  instruments  to  order  only.     See  page  197. 
Code  Word  —  Beaman  Price,  extra  $3O.OO 


No.  Ic,  Style  o. 


The  Berber  Double  Opposite  Vernier  Attachment  for  transits  pro- 
vided with  a  5-incii  full  vertical  circle,  verniers  reading  to  minutes.  For  more  in- 
formation and  adjustments  of  this  feature  see  page  49.  Made  to  order  only. 

Code  Word  —  Bowek  Prijce,  extra  $2O.O() 

For  price  of  Double  Opposite  Vernier  Attachment  with  Open  Frame  protected 
vertical  circle,  graduation  glass-covered,  see  page  199. 

Reversion  Level. 


Code  Word— Bowis 


Applicable  to  any  of  our  Transits  of  sizes  Xo.  1,2   3,  4,  5  and  6. 

Price,  extra  (over  price  of  transit  with  level  attachment  to  telescope), 


$12.OO 


NOTE.— This. level  has  a  revolvable  cover  guard  to  protect  the  exposed  side  of  the  level  and  to  act  as  a 
reflector  while  in  use. 

The  adjustment  of  this  level  and  the  horizontal  cross-wire  has  to  be  made  in  the  manner  described  for 
the  fixed  level  attached  to  the  transit  telescope,  see  pages  54  and  63. 


No.  1  c,  Style  p. 

in.  at  edge  of  jrraduatio 


Tachymeter.* 

For  size  and  particulars,  as  well  as  for  extras,  see  pp.  15O-153. 

No.  1  c,  Style  p.     Graduations  of  horizontal  and  vertical  circles  on  solid  silver, 
reading  to  minutes;  6-inch  full  vertical  circle  with  two  double  opposite  verniers  read- 
ing to  minutes ;  glass  shades  over  verniers;  3|-inch  striding  level;  gradienter attachment; 
fixed  stadia  wires;  etc.     Standards  leather  finished. 
Code  Word,  Buckwheat.  Price  as  above,  $296.OO 

This  instrument  without  a  striding  level. less,     $20.00 

*'  "  "        double  opposite  verniers  for  vertical  circle,  but  with  a  double 

vernier  between  the  legs  of  the  standard  as  in  No.  Ic,  page  154 .         .         less,     $16.00 

*The  name  7^achynteter,  or  rapid  measurer,  has  been  applied  for  many  years,  in  Europe  to  instruments  of 
this  description.  The  characteristic  of  tachymetry  is,  that  all  the  data  required  for  the  location  of  points  are 
rapidly  determined  by  the  instrument,  by  means  of  horizontal  and  vertical  angles,  and  stadia  measurements 
of  distance. 


157 


No.  1  d. 

As  made  by  C.  L.  Berger  &  Sons. 


Tachymeter. 

For  size  and  particulars  of  this  instrument  see  pages  15O-153. 

!N"o.  1  d,  as  in  cut,  graduation  of  horizontal  circle  on  solid  silver,  opposite  verniers 
reading  to  20";  graduation  of  vertical  arc  on  solid  silver,  verniers  reading  to  minutes; 
glass  shades  over  verniers;  detachable  reading  glasses  for  both  circles,  11^-inch  tele- 
scope showing  objects  inverted,  power  27  diameters;  3^-inch  striding  level;  gradienter 
attachment;  fixed  stadia  wires;  etc.  Standards  leather  finished. 
Code  Word,  Bumelia.  Price,  as  above,  $312.OO 

No.  1  d,  as  in  cut  above,  and  as  described  under  No.  1  d  "Bumelia"  but  with  full 
vertical  circle  protected  by  an  aluminum  guard  as  shown  in  No.  1  c,  page  154. 

Code  Word,  Burton.  Price,  $321.OO 

This  instrument  without  a  detachable  reading  glass  to  the  vertical  arc,  less  $5.00 

NOTE. —  For  a  description  of  the  striding  level,  its  use  and  adjustment,  see  page  56.  This  striding  level 
and  the  detachable  reading  glasses,  as  shown  above,  can  be  attached  only  to  our  transits  of  the  above  descrip- 
tion; we  cannot  attach  them  to  instruments  already  made. 


158 


.  1  f. 

is  made  by  C.  L.  Berger  &  So 


Tacliymeter. 

With  three  Leveling  Screws  and  Shifting  Center. 

No.  1  f  ^  as  in  cut.  Graduation  of  horizontal  circle  on  solid  silver,  opposite  ver- 
niers reading  to  20'' ;  graduation  of  5  inch  vertical  arc  on  solid  silver,  verniers  reading 
to  minutes;  glass  shades  over  verniers ;  detachable  reading  glasses  for  horizontal 
circle ;  ll|-inch  telescope  showing  objects  inverted,  power  27  diameters ;  6- inch  spirit 
level  parallel  to  telescope ;  3^  inch  striding  level ;  gradienter  attachment ;  fixed  stadia 
wires,  etc.  Standards  leather-finished.  Price,  as  above,  $322.QO 

For  size  and  particulars  of  this  instrument,  as  well  as  for  Extras  see  pages  i5°-i53- 
For  adjustment  of  Transverse  striding-level  resting  on  special  collars  see  page  56- 

Code  word     Burdock. 


159 
C.  !L.  BEBGER  &  SONS 


No.  1  g. 

in.  at  edge  of  graduation.) 


Tacliymeter. 

For  size  and  particulars  of  tlie  above  instruments,  as  well  as  for  extras,  see  pp.  15O-153. 

NO.  1  g",  as  in  cut.  Same  as  No.  1  f ,  but  having  a  5-inch  full  vertical  circle  with  two 
double  opposite  verniers  reading  to  minutes,  and  two  reading-glasses  to  tJxe  vertical 
circle. 


Code  Word,  Buttercup. 


Price  as  above,  $352.OO 


160 

C.   L.  BEKGEK  &  SONS. 


MONITOR  TYPE 
Engineers'  Transit  No.  1  m. 

With  Yoke  Standards  and  Wye-Bearings.    Without  Compass. 
For  Triangulation,  General  Construction,  Tunnel  and  all  classes  of  Underground  Work. 

In  the  Transit  illustrated  on  opposite  page  the  yoke-shaped  standard  frame  carrying 
the  wye-bearip^s  for  the  telescope's  axis  of  revolution,  is  cast  in  one  piece,  and  its  form, 
being  of  superior  design,  is  such  as  to  give  great  upright  and  lateral  stiffness,  with  compara- 
tive lightness  in  weight.  This  fact,  coupled  with  the  desire  to  have  an  instrument  free 
from  the  defects  so  often  noticed  in  the  Transits  enumerated  under  Nos.  1  and  2, 
etc.,  with  compasses  where  the  necessary  lateral  rigidity  of  the  standards  must  be  obtained 
by  the  peculiar  conically-shaped  pivot  ends  of  the  telescope's  axis  of  revolution,  at  the 
expense  of  accuracy,  led  us  to  adopt  the  cylindrical  form  of  pivots  resting  in  wye 
bearings,  to  ensure  a  true  motion  of  the  telescope  in  the  vertical  plane,  (one  that  is 
free  from  any  deflection  of  the  line  of  sight  caused  by  wabbling  in  bearings  loose  from 
wear  and  lateral  strain).  In  this  Transit  the  telescope  reverses  only  through  the  standard, 
as  usual,  the  aim  being  to  furnish  a  Transit  most  eminently  fitted  for  the  highest  class 
of  engineering  work  of  all  kinds,  but  at  a  cost  lower  than  those  enumerated  later  on  under 
Triangulation  Transits.  In  this  instrument  the  wye-bearings  are  well  protected  from 
dust  and  water.  The  main  plate  level  is  placed  in  the  center  of  the  upper  plate,  where 
it  is  entirely  protected  by  the  base  of  the  standard  frame  and  by  the  aid  of  a  special  guard, 
and  where  it  can  easily  be  read  from  both  sides.  The  upper  surface  of  the  vernier  plate 
is  slanting  downwards,  and  the  vernier  openings  are  raised  above  the  surface,  and  special 
channels  are  provided,  so  that  water  will  run  off  immediately.  The  Yoke  standard  frame 
will  be  leather-finished.  In  this,  as  in  all  other  instruments,  the  fine  appearance  and 
general  character  depends  principally  on  simplicity  of  design,  coupled  with  tine  work- 
manship, and  a  high  state  of  efficiency  of  every  part.  Other  parts  that  cannot  easily 
be  finished  and  lacquered  in  the  usual — but  mostly  antiquated — manner,  are  therefore 
also  leather-finished.  This  is  in  line  with  good  taste  and  modern  thought  and  im- 
provements, to  enable  us  to  unite  as  many  pieces  as  possible  to  secure  great  stability 
and  steadiness  under  all  conditions  in  order  to  arrive  at  quick  and  thoroughly  reliable 
results. 

Transit  Xo.  1  in,  as  in  cut  (for  size,  weight  and  particulars,  see  Transit  No.  1, 
page  142);  graduation  of  horizontal  circle  on  solid  silver,  double  opposite  verniers 
reading  to  30";  'graduation  of  5-inch  vertical  circle  on  solid  silver,  double  vernier 
reading  to  minutes;  aluminum  guard  to  vertical  circle;  glass  shades  over  verniers; 
Ill-inch  erecting  telescope  with  lj-inch  aperture;  power  24  diameters;  long  spirit- 
level  to  telescope;  fixed  stadia  wires;  etc.  Made  to  order  only. 

Price,  as  above  $265.OO 

C^de  Word Buxana 

This  transit  can  be  made  with  inverting  telescope  when  so  ordered;  length  12  inches, 
clear  aperture  If  inches,  power  28  diameters.  No  extra  charge. 

If  desired  with  inverting  telescope  add  to  the  Code  word  "  Invert." 

Oblong  Compass  permanently  fastened  to  and  within  the  confines  of  vernier  plate 

at  side  of  standard.     The  3-inch  needle  can  be  read  5°  each  side  of  the  zero  of  the 

graduation. 

Cotle  Word— Oblong.  Price  extra,  $15.OO 


1G1 
C.  L.  BEKGER  &  SONS. 


.  at  edge  of  graduation.) 


Engineers'  Transit  No.  1  m. 

With  Yoke  Standards  and  Wye-Bearings.     Without  Compass. 
For  Triangulation.  General  Construction,  Tunnel  and  all  classes  of  Underground  Worn. 


162 

64     SURVEYORS'  TRANSIT  No.  1  s. 

With  Compass,  Yoke  Standards  and  Wye-Bearings. 

It  is  well  known  that  in  Transits  with  compass  (styles  Nos.  1,  2,  3, 4,  5  and  6)  the 
strength  required  for  the  standards  to  support  the  telescope,  and  to  prevent  the  latter  from 
shifting  laterally  in  the  bearings,  is  derived  mainly  from  the  vernier  plate  and  its  compass 
ring  as  a  base,  from  the  rigidity  ot  the  standards  themselves  and  their  width  apart,  and 
last  —  but  most  important  —  from  the  peculiar  shape  of  the  pivot-ends  of  the  horizon- 
tal axis  of  revolution,  which  latter  prevents  both  of  the  standards  from  swaying  to  and 
fro.  Ingenious  and  time-honored  as  this  construction  is  —  being  exemplified  in  many 
thousands  of  instruments  —  it  cannot  compare  in  degree  of  accuracy  with  that  afforded 
when  the  ends  ot  the  telescope's  axis  are  of  cylindrical  form  running  in  wye-bearings,  pro- 
vided the  necessary  upright  and  lateral  stiffness  can  be  obtained  in  the  standard  frame. 
The  Yoke  standard  frame,  shown  in  the  cut  on  opposite  page,  is  of  great  strength  com- 
bined with  lightness,  and  enables  to  successfully  mount  the  telescope's  axis  by  means 
of  cylindrical  pivots  in  wye-shaped  bearings.  The  motion  of  the  telescope  in  the  vertical 
plane  is  therefore  entirely  free  from  such  defects,  as  deflection  of  the  line  of  sight,  etc., 
noticed  in  the  older  styles,  when  caused  by  wear  and  strain.  To  obviate  this,  has  been 
the  object  of  introducing  the  yoke  frame  —  common  in  all  our  triangulation  Transits 
—  but  having  a  compass  mounted  in  the  central  portion  of  its  base.  With  this  arrange- 
ment the  surveyor  is  now  placed  in  possession  of  an  instrument  whose  chief  features 
have  no  superior  in  point  of  accuracy,  fine  workmanship  and  thorough  adaptation  to  his 
needs.  The  telescope  reverses  through  the  standards  only.  The  Yoke  frame  will  be 
leather-finished;  all  other  parts  will  be  polished  and  lacquered.  The  whole  instrument 
has  a  fine  appearance. 

Transit  No.  1  S,  as  in  cut  (for  size,  weight  and  particulars,  see  Transit  No.  1 , 
page  150);  graduation  of  horizontal  circle  on  solid  silver,  double  opposite  verniers 
reading  to  minutes;  5-inch  vertical  circle  with  one  double  vernier  reading  to  minutes,  at 
eye-end;  graduation  on  solid  silver;  aluminum  guard;  glass  shades  over  verniers;  llf-inch 
erect  telescope  with  1^-inch  aperture,  power  24-  diameters,  long  spirit-level  to  telescope; 
fixed  stadia  wires;  3T9^-inch  magnetic  needle  with  variation  plate;  etc. 

Made  to  order  only. 

Price $3OO.OO 

Code  Word Buxota. 

Extras  to  Transit  No.  1  s. 

Horizontal  circle  graduated  to  read  to  SO",  extra        .  .10.00 

"      "     "  20"      "  .  20.00 

This  transit  can  be  made  with  inverting  telescope  when  so  ordered;  length  12  inches, 
clear  aperture  1  f  inches,  power  28  diameters.  No  extra  charge. 

If  desired  with  inverting  telescope  add  to  the  code  word   "  Invert." 


5s"  SURVEYORS'  TRANSIT  No.  2  s. 

Horizontal  circle  5%  in.  at  edge  of  graduation. 

Tnaiisit  No.  2  s  (size,  weight -and  particulars  as  in  No.  2,  page  168),  but  with 
magnetic  needle  2*/£"  long,  variation  plate;  otherwise  with  same  features  as  for 
No.  1  S  above.  Made  to  order  only 

Price $3OO.OO 

Codeword Buylis. 

This  instrument  with  inverting  telescope,  add  to  the  Code  Word  "Invert." 

Transits  No.  1  s  and  No.  2  s,  enumerated  above,  may  have  a  5"  vertical 
arc,  with  the  verniers  between  the  Yoke  standard  frame  instead 
of  the  full  vertical  circle  with  the  verniers  at  eye  end. 

Price  $280.00 

Code  Word,  Transit  No.  Is .       Buzada. 

"        Transit  No.  2s Buzemo. 

For  prices  of  solar  attachments,  etc.,  see  pages  172  to  175. 


Patented. 

(6J4  in.  at  edge  of  graduation.) 


Surveyors'  Transit  No.  1  s. 

"With  Compass,  Yoke  Standards  and  "Wye -Bearings. 

(Above  instrument  is  shown  with  inverting  telescope.) 


164 

C.  L.  BERGER  &  SONS,  BOSTON 


5^"   ENGINEERS'  AND  SURVEYORS'  TRANSIT* 

A  Standard  Size  of  less  weight  than  transit  No.  1,  but  larger  than  size  No.  2. 
The^  telescope  has  nearly  the  same  power  as  No.  1  Erecting1  and  when  made 
Inverting"  is  more  powerful. 

The  outer  or  contra  clockwise  row  of  figures  on  the  horizontal  circle  and 
those  of  the  verniers  of  the  right  side  of  verniers  A  and  B  can  be  furnished  in  Red 
but  will  be  made  to  order  only,  see  cat.  page  41.  Instrument  stands  upright  in 
carrying  case. 


Transit,  Size  No. 

SPECIFICATIONS  :  — 

Horizontal  circle  51/£-iiieh  (at  edge  of  graduation),  graduated  on  heavy 
ring  of  solid  silver,  double  opposite  verniers,  read  to  minutes,  two  rows  of 
figures  0  to  360  in  opposite  directions;  figures  inclined  in  the  direction  verniers 
should  be  read,  verniers  at  30°  to  line  of  sight. 

Vertical  circle  5-inch,  graduated  on  solid  silver,  double  verniers  read  to  min- 
utes, between  legs  of  standard,  and  Aluminum  Guard. 

Telescope  lOM»-incll,  objects  erect,  f  aperture  114  inch,  power  2O  dia. 

Stadia  wires,  fixed,  in  ratio  1  :100. 

Spirit-level  5!4-inch,  with  clamp  and  tangent  screw  to  telescope. 

Plate-levels  of  standard  length  and  very  sensitive. 

Magnetic  needle  3!£-inch,  edge-bar  form.    (See  pages  98-99.) 

Shifting  center,  to  set  instrument  exactly  over  a  given  point. 

Punch  mark  on  top  of  telescope,  to  enable  to  center  the  transit  from  a  point  above. 

Transit  leatheri  zed  (see  page  9).  All  important  parts  treated  in  our  durable 
and  handsome  leather  finish. 

Full  length  split-leg  tripod. 

The  Mahogany  case  has  a  leather  strap,  hooks,  etc.     It  contains  a  sun-shade, 

a  wrench,  a  screw-driver,   an  adjustable  plumb-bob,   a  magnifying  glass,   an  ad- 

justing pin,  and  weighs  about  7  Ibs. 

Weight  of  transit  about  13  Ibs.;  weight  of  tripod  from  9  to  9}/£  Ibs. 

Gross  weight  of  transit  packed  securely  for  shipment  in  two  boxes,  about  55  Ibs. 

Code  Word,  Cakula.  Made  to  order  only.    Price  $252.OO 


as  above,  with  a  5-inch  Arc  in  place  of  a  full  Vertical  Circle. 
Code  Word,  Cagana.  Made  to  order  only    Price,  $243.OO 

Transit   as  under  Cagana,  but  without  arc. 

Code  Word,  Cadagon.  Price,  $223.OO 

Extras  to  Transit  No. 


Graduation  of  Horizontal  Circle,  reading  to  30"  .... 

Gradienter  attachment  .  .  .  . 

Offsetting  arrangement  ........ 

Variation  Plate,  adapted  for  all  declinations  E.  or  W.     .... 

Extension  Tripod,  in  addition  to  the  split-leg  tripod  furnished  with  the  transit 
Plain  Prism,  with  colored  glass,  for  observing  the  sun's  altitude  (fig.  7),  page  175 


$10.00 
5.00 

10.00 
19.50 
8.00 

Improved  Prism,  with  colored  glasses,  for  observing  the  sun's  altitude  (fig.  5),  page  175   .         12.00 
Davis'  Solar  Attachments,  screen  with  improved  prism  mounting  (page  175) 
Berger's  Solar  Attachment  (small)  (pages  172  and  173)  .  .  •  •  .        52.00 

"         Latitude  Level  Attachment       .  . 

Short  Focus  Lens  Attachment  (see  pages  101  and  203)    .  .  .         One  $8.50,  pair        16.00 

Leather  Cover  over  case  arranged  to  be  strapped  to  a  saddle  of  a  horse 

"  "         "        "    as  above  with  shoulder  straps     ......         15.00 

Cravenette  hood  (heavy,  gives  good  protection)  silk  (light,  not  waterproof),  each  . 

Bottle  of  fine  watch  oil,  for  the  centers,  etc.,  of  transit         .  .    -      0.35 

*Unusual  size;  see  our  No.  51/?  Monitor  Transit,  pages  166  and  167. 

fAn  Inverting  Telescope  of  1W  aperture,  lO'/a"  long,  power  23  dia.  can  be  supplied 
with  the  above  transit  in  place  of  the  regular  erecting  one  at  no  additional  cost.  This  telescope  is 
particularly  well  adapted  for  stadia  work.  Made  to  order  only. 


1G5 
C.  L.  BEBGER  &  SONS,  BOSTONo 


No.  51/2. 

in.  at  edge  of  graduation 


Patented. 


No.  5!4  Engineers'  and  Surveyors'  Transit. 

Unusual  size,  made  to  order  only.     (See  No.  5%  complete  Monitor  Transit, 
pages  166  and  167.) 

For  size,  weight,  particulars  and  extras  of  this  instrument  see  opposite  page. 

Code  word  Cakula  Price,  $252.OO 

The  Front  Plate  Level  is  fully  protected  its  entire  length  by  an  aluminum  guard 
which  is  independent  of  the  level  and  its  adjustments. 

To  avoid  mistakes  and  to  save  time  telegraph  Code  name. 


166 

C.  L.  BERGER  &  SONS.  BOSTON 

5|"     MONITOR  TYPE 
Engineers'  and  Surveyors'  Transit 

With  Compass.  Cylindrical  Pivots  to  Telescope  Axis.  Wye-Bearings. 

A  Standard  Size  of  less  weight  than  transit  No.  1 ,  but  larger  than  sizeNo.2. 

In  general  use  for  accurate  WOl'k  in  cities  where  commercial  traffic  prevails,  in 
and  about  factories  and  erection  of  buildings.  For  underground  work  it  has  .no  supe- 
rior. The  telescope  has  nearly  the  same  power  as  No.  1  Erecting1  and  when 
made  Inverting'  is  more  powerful.  Modern  design,  ruggedness  of  construction, 
and  its  great  lateral  rigidity  of  standards  for  steadying  the  tel- 
escope's axis  place  this  style  on  a  par  with  our  Yoke  Standard  Frames, 
enumerated  later  on,  commending  it  to  all  requiring  uninterrupted  and  efficient 
service  in  strenuous  work. 

The  outer  or  contra  clockwise  row  of  figures  on  the  horizontal  circle  and  those  of 
the  verniers  of  the  right  side  of  verniers  A  andB  can  be  furnished  in  Red  but  will  be 
made  to  order  only,  see  cat.  page  41.  Instrument  stands  upright  in  carrying  case. 


Monitor  Transit,  Size  No. 

SPECIFICATIONS  :— 


Horizontal  circle  5^  iiicli  (at  edge  of  graduation),  graduated  on  heavy 
ring  of  solid  silver,  double*  opposite  verniers,  read  to  minutes,  two  rows  of 
figures  0  to  360  in  opposite  'directions;  figures  inclined  in  the  direction 
verniers  should  be  read,  verniers  at  30  degrees  to  line  of  sight. 

Vertical  arc  5-iiich,  graduated  on  solid  silver,  double  verniers  read  to  minutes. 

Telescope  lO^-incli,  objects  erect,  i    aperture  l^-inch,   power  2O  dia. 

Stadia  wires,  fixed,  in  ratio  1  :  100. 

Spirit  level  5  >2  -inch,  with  clamp  and  tangent  screw  to  telescope. 

Plate  levels  of  standard  length  and  very  sensitive. 
'Magnetic  needle  3>£-incIi,  edge-bar  form.  (See  pages  98-99.) 

Shifting"  center,  to  set  instrument  exactly  over  a  given  point. 

Punch  mark  on  top  of  telescope,  to  enable  to  center  the  transit  from  a  point  above. 

Transit  leather  ized  (see  page  9).  All  important  parts  treated  in  our  durable 
and  handsome  leather  finish. 

Full  length  split-leg-  tripod. 

The  Mahogany  case  has  a  leather  strap,  hooks,  etc.  It  contains  a  sun-shade, 

a  wrench,  a  screw-driver,  an  adjustable  plumb-bob,  a  magnifying  glass,  an  ad- 

justing pin,  and  weighs  about  7  Ibs. 

Weight  of  transit  about  13  Ibs.;  weight  of  tripod  from  9  to  9)4  Ibs. 

Gross  weight  of  transit  packed  securely  for  shipment  in  two  boxes,  about  55  Ibs. 

Code  word  Caboa  Price,  $243.OO 

Transit  as  above,  but  in  place  of  arc  with  a  5-inch  full  Vertical  Circle 

and  Aluminum  Guard  double  verniers  between  legs  of  standard. 
Code  word  Cafid  Price  $252.OO 

Extras  to  Monitor  Transit  No. 

Graduation  of  Horizontal  Circle,  reading  to  30" 

Gradienter  attachment  .  •  ?• 

Offsetting  arrangement  .  •  ... 

Variation  Plate,    adapted  for  all  declinations  E.  or  W.  ,'..•.  '  .         '  '        in  en 

Extension  Tripod,  in  addition  to  the  split  leg  tripod  furnished  with  the  transit       . 

Plain  Prism,  with  colored  glass,  for  observing  the  sun's  altitude  (fig.  7),  page  175  .          8.00 

Improved  Prism,  with  colored  glasses,  for  observing  the  sun's  altitude  (hg.  5),  page  175        12  .uu 

Davis'  Solar  Attachments,  screen  with  improved  prism  mounting  (p.  175) 

Berber's  Solar  Attachment  (small)  (pp.  172  and  173)  •        o2.w 

Latitude  Level  Attachment 

Short  Focus  Lens  Attachment  (see  pages  101,  203)  .        One  $8.50,  pair 

Leather  Cover  over  case  arranged  to  be  strapped  to  a  saddle  of  a  horse         .  .        it-yv 

"  ««          "       "as  above  with  shoulder  straps    .  •          V'XX 

Cravenette  hood  (heavy,  gives  good  protection),  silk  (light,  not  waterproof),  each  .          i.w 

Bottle  of  fine  watch  oil,  for  the  centers,  etc.,  of  transit         ..... 

"This  transit  can  be  furnished  with   a  single  B  vernier,  see  Monitor  Type  transit  No.  4  1A, 
page]180.      Made  to  order  only. 

t  An  Inverting  Telescope  of  ±1/4"  aperture,  Id/a"  long,  Ppwer  23  dia.  ^n  be  supplied 
with  the  above  transit  in  place  of  the  regular  erecting  one  at  no  additional  cost.     J 
particularly  well  adapted  for  stadia  work.     Made  to  order  only. 


167 

C.  L.  UKlttiKK,  &  SONS.   BOSTON 


Patented. 


No.  5  y?  Complete  Monitor  Type  Transit 

For  si/.e,  weight,  particulars  and  extras  of  this  instrument  see  opposite  page. 


Code  word  Caboa 


Price,  $243.OO 


Cylindrical  Pivots  to  telescope's  axis  running  in  the  improved.  Wye  bearing.  The 
center  point  is  located  on  a  round  hub  on  the  telescope's  axis  to  better  distinguish  it  in 
dark  places  when  centering  under  a  point  above  the  transit. 

The  Eye  Piece  Cap  is  large  in  diameter.  It  affords  a  protection  to  the  eye  of  the  ob- 
server in  a  glaring  sun.  It  has  been  combined  with  a  dust  guard  which  fully  protects 
the  Eye  Piece  focussing  slide. 

The  Front  Plate  Level  is  fully  protected  its  entire  length  by  an  aluminum  guard 
which  is  independent  of  the  level  and  its  adjustments. 

Improved  Levelling  Head  with  dust  caps  to  levelling  SCI-CAVS. 

To  avoid  mistakes  and  to  sat'e  time  telegraph  Code  name. 


168 

5|"  ENGINEERS'  AND  SURVEYORS'  TRANSIT. 

The  essential  features  of  this  transit  are  like  those  enumerated  under  No.  1, 
page  150,  \vith  the  exception  of  size  and  weight.  We  strongly  recommend  it  for 
use  where  a  lighter  instrument  is  desirable  for  land  surveying,  railroad,  mining  and 
underground  work,  etc.,  of  all  kinds  and  where  a  graduation  reading  direct  to  single 
minutes  and  to  30"  and  20"  by  estimation  is  preferred.  Every  part  is  made  with  great 
care  and  the  aperture,  focal  length  and  power  of  telescope  are  properly  related  to  each 
other  and  to  the  size  of  plate  to  make  this  a  very  compact,  portable  and  accurate  transit.* 

Complete  Transit  Size  No.  2.  As  in  cut  (see  opposite  page),  but  with 
verniers  at  30°  to  line  of  sidit  (unless  ordered  to  be  at  90°). 


Horizontal  circle  5>^-inch  (at  edge  of  graduation),  graduated  on  heavy  inlaid 
ring  of  solid  silver,  double  opposite  verniers  reading  to  minutes,  two  rows  of 
figures  0  to  360  in  opposite  directions;  figures  inclined  in  the  direction  verniers 
should  be  read;  verniers  at  30°  to  line  of  sight. 

Vertical  arc  5-inch,  graduated  on  solid  silver,  double  verniers  read  to  minutes. 
Telescope  lOX-inell,  Objects  erect,  t  aperture    1#  inch, -power  18  dia. 
Stadia  wires,  fixed,  in  ratio  1:100. 

Spirit  level  5>£-inch,  with  clamp  and  tangent  screw  to  telescope. 
Plate  levels  of  standard  length  and  very  sensitive. 
Magnetic  needle  3%"   edge-bar  form  having  no  index  error. 
Shifting"  center,  to  set  instrument  exactly  over  a  given  point. 
Punch  mark  on  top  of  telescope,  to  enable  to  center  the  transit  from  a  point  above. 
Standards  leather ized  (see  page  9). 
Full  length  split-leg-  tripod. 

The  Mahogany  case  has  a  leather  strap,  hooks,  etc.  It  contains  a  sun-shade,  a  wrench, 
a  screw-driver,  an  adjustable  plumb-bob,  a  magnifying  glass,  an  adjusting  pin,  and 
weighs  about  7  Ibs. 

Weight  of  transit  about  10  Ibs. ;  weight  of  tripod  from  9  to  9>^  Ibs. 

Gross  weight  of  transit  packed  securely  for  shipment  in  two  boxes,  about  55  Ibs. 

Code  Word  Calypso.  Price,  $243.OO 

Transit  No.  2  as  in  Calypso  but  without  solid  silver,  graduations  silvered. 

Code  Word  Calixa.  Price,  $228.OO 

Transit  No.  2  as  in  Calypso  but  -without  vertical  arc  (  see  No,  1  a,  page  152). 

Code  Word  Calamus.  Price  $223.OO 

Transit  No.  2  as  in  Calypso  but  -without  level,  clamp,  tangent  screw,  arc 
or  stadia  -wires  to  telescope  (see  cut  Plain  Transit  No.  1,  page  151). 

Code  Word  Caladium.  Price  $19O.OO 

Extras  to  Complete  Transit  No.  2. 

Standards  polished  and  lacquered  (no  leather  finish).  Extra 95. OO 

5-inch  full  vertical  Circle*,  in  place  of  arc),  graduation  on  solid  silver,  double  vernier 

between  legs  of  standard  reading  to  minutes,  with  aluminum  guard  (as  in  cut,  page  177).    .         .  9.0O 

Gradienter  attachment 5.OO 

Offsetting  arrangement 5.0O 

Short  FOCUS  Lens  (see  pp.  101,  203).     One  pair 16.OO 

Variation  Plate,  to  set  off  all  declinations  E.  or  \V 1O.OO 

Cravenette  hood  (heavy,  gives  good  protection);  Silk  (light,  not  waterproof),  each    .        .  1.00 

Bottle  Of  fine  watch-oil,  to  lubricate  the  center,  etc.,  of  transit O.35 

*For  close  stadia  work,  Transit  telescope  size  No.  1,  with  its  longer  focal  length  and  higher  power,  will 
be  best  suited  for  that  purpose.  But  in  all  cases  where  greater  lightness  and  portability  and  where  only  general 
good  results  in  stadia  work,  as  obtained  with  a  less  powerful  telescope,  will  be  deemed  satisfactory,  size  No.  J8 
should  be  chosen.  We  cannot  put  a  telescope  of  the  size  described  under  No.  i  upon  a  Transit  size  No.  2. 

t  An  Inverting  Telescope  of  1%"  aperture,  1O%  inches  long  and  with  a  power  of  22  dia.  can 
be  supplied  with  the  above  transits  in  place  of  the  regular  erecting  one  at  no  additional  cost,  but  the  in- 
strument  must  be  made  to  order.  This  telescope  is  particularly  well  adapted  for  stadia  work. 


169 
C.  L.  BERGEK  &  SONS. 


No.  2. 

n.  at  edge  of  graduation) 


5-inch  Complete  Engineers'  and  Surveyors'  Transit. 

For  size,  weight,  particulars  and  extras  of  this  instrument  see  opposite  page. 

Transit  Xo.  2,  as  already  described  on  opppsite  page  —  Calypso— and  as  shown 
above,  but  with  verniers  at  3O°  to  line  of  sight  (unless  ordered  to  be  at  90°),  grad- 
uations on  solid  silver,  fixed  stadia  wires. 

Code  word,  Calypso.  Price  $243.OO 

(For  code  words  for  Extras  and  chauges  from  Calypso, 
see  pages  C,  E  and  F  of  complete  code  at  back.) 

NOTE  —  If  verniers  are  desired  at  90°  to  line  of  sight,  as  in  cut  above,  the  instrument 
must  be  made  specially,  — no  extra  charge. 


The  Surveyors'  Solar  Attachment. 

Placed  on  the  side  of  the  transit  it  permits  the  main   telescope  to  be  reversed  through 

the  standards  at  all  times. 

Our  Surveyor's  Solar  Attachment,  or  meridian  finder,  is  in  principle  like  Pear- 
son's (made  by  us  heretofore),  not  requiring  computation,  but  instead  of  the  lens-bar 
it  has  a  small  telescope  with  £-inch  aperture  and  6  inches  focal  length.  This  telescope 
is  provided  with  a  detachable  prism  and  colored  glass  for  the  eye-piece,  and  also  a  plain 
colored  glass  for  use  with  the  main,  or  solar  telescope,  and  our  customary  solar  square 
as  in  figure  RK,  page  122. 

This  solar  attaches  by  means  of  a  screw  to  the  end  of  the  cross-axis  of  the  transit 
telescope  on  the  side  of  the  clamp  and  tangent-screw,  as  shown  in  the  cut,  and  when 
not  in  use  can  be  again  readily  detached  from  the  instrument  proper.  It  has  no  dec- 
lination arc.  The  declination  of  the  sun,  and  the  latitude  of  the  place  of  observation 
are  both  set  by  the  vertical  circle  of  the  transit.  All  settings  for  position,  viz.,  that 
of  the  polar  axis  for  latitude,  that  is,  for  coincidence  with  the  zero  marks  of  the  vertical 
circle  and  verniers,  and  the  setting  of  the  declination,  are  secured  by  two  spirit  levels 
placed  upon  the  polar  axis  and  upon  the  solar  telescope,  as  will  be  seen  in  the  cut. 
The  degree  of  precision  attainable  and  the  ease  of  manipulation  in  the  use  of  this 
attachment  is  commensurate  with  that  of  our  engineers'  and  surveyors'  transit. 

To  determine  true  meridian  at  any  hour  of  a  day,  it  is  only  necessary  that  the 
declination  and  refraction  of  the  sun  on  that  particular  day  and  hour  be  known  to  the 
observer,  and  that  the  polar  axis  be  raised  precisely  to  the  co-latitude  of  the  place  of 
observation. 

By  the  use  of  our  Latitude  Level  (also  attaching  to  the  cross-axis  at  the  side 
of  the  vertical  circle,  as  shown  in  the  second  cut),  not  requiring  a  reading  of  the  ver- 
tical circle  for  eveiy  setting  of  the  polar  axis  for  latitude  except  once  in  a  day,  obser- 
vations can  be  made  repeatedly  with  speed  and  accuracy.  With  the  declination  and 
refraction  of  the  sun  previously  worked  out  for  the  various  hours  of  a  day,  observa- 
tions can  be  made  nearly  as  fast  as  a  needle  can  be  read  of  the  surveyor's  compass. 

A  concise  description  of  both  attachments  will  be  found  in  our  manual.  The  ac- 
companying illustrations  of  the  solar  attachment  represent  them  as  applied  to  transits 
No.  1  and  No.  2.  Of  all  the  different  kinds  in  use,  we  believe  it  to  be  the  most 
efficient.  Owing  to  its  position  at  the  side  of  the  transit,  it  can  be  easily 
manipulated.  The  adjustments  are  few  and  simple,  and  need  to  be  verified  only 
from  time  to  time ;  besides,  they  can  be  readily  proved  and  perfected,  being  similar  to 
those  in  the  transit. 

Weight  of  this  Solar  attachment  is  1  lb.,  that  of  the  latitude  level  about  £  Ib. 
Both  are  packed  in  a  separate  box  of  mahogany  provided  with  a  shoulder  strap, 

and  can  also  be  packed  in  the  box  with  the  instrument. 


Price  of  Solar  attachment,  as  above,  with  counterpoise,  prism  with  colored 
glasses  and  additional  colored  glass  to  apply  to  the  telescope  of  the  transit  to 
observe  the  sun's  altitude,  in  order  to  apply  the  correction  for  refraction  in 
solar  transit  work,  .  ...,,....  $85.OO 


Price  of  latitude  level,  as  above,  .,„....  15.OO 

Surveyors'  Solar  Attachment  (Smith  Solar),  as  used  by  "  General 
Land  Office  of  U.  S.  A.,"  attached  to  transits  No.  1-s  and  No.  2-s  on  pages 

•       162  and  163  as  well  as  the  4^"  transit  of  the  same  style. 

Complete  Transits  No.  1-s,  No.  2-s  and  No.  4!£-s  with  Smith 
Solar, Price,  $363.OO 


171 

C.  L.  BERGER  &  SONS. 


Surveyors'  Solar  Attachment. 


Latitude  Level  Attachment. 

Shown  as  applied  to  a  Transit  with  Solar  Attachment. 

NoTE.-The  surveyors'  solar  attachment  and  our  latitude  level  can  be  placed  only  upon  Transits  No. 
No.  2,  and  No.  3,  and  then  only  when  ordered  with  the  instrument. 


172 

The  Berger  Solar  Attachment 

Attachable  to  Transits,  Sizes  1,  5'/2,  2,  4 '/a  and  4,  having  a  Full  Vertical  Circle. 
For  U.  S.  Deputy  Surveyors,  Surveyors  and  Mining  Engineers. 

This  Solar  Attachment  may  be  used  as  a  first-class  solar  in  surface  surveying  for 
determining  meridian.  The  solar  telescope  being  longer  and  more  powerful  than 
heretofore,  and  as  its  horizontal  axis  is  provided  with  our  patented  lateral  adjust- 
ment *  (see  cuts  a,  a  on  right-hand  side  of  illustration),  we  are  enabled  to  place  its 
line  of  collimation  so  truly  above  that  of  the  main  telescope  as  to  be  exactly  in  the 
same  vertical  plane. 

As  a  solar  attachment,  or  meridian  finder,  it  is  in  principle  like  Pearsons'  and  that 
formerly  made  by  us  (see  cut  page  65),  not  requiring  computation;  but  instead  of  the 
lens  bar,  or  small  telescope,  f  it  is  now  constructed  with  a  telescope  of  one-inch  aperture 
and  six-inch  focal  length,  provided  with  a  diagonal  eye-piece,  colored  glass  and  wires 
arranged  in  a  square,  as  shown  on  next  page  and  described  on  page  71. 

This  solar  attachment  fastens  by  means  of  a  screw  to  the  cross  axis  of  the  transit 
telescope.  It  has  no  declination  arc.  The  declination  of  the  sun  and  the  co-latitude 
of  the  place  of  observation  are  both  set  off  by  the  vertical  circle  of  the  transit.  All 
settings  for  position,  viz.  that  of  the  polar  axis,  to  be  truly  at  right  angles  to  line  of 
sight  of  main  telescope  and  the  setting  of  the  declination,  are  secured  by  the  spirit 
level  attached  to  the  solar  telescope.  The  degree  of  precision  and  simplicity  of  manipu- 
lation attained  thereby  is  commensurate  with  that  of  our  Engineers'  Transit. 

To  determine  true  meridian  at  any  hour  of  the  day  it  is  only  necessary  that  the 
declination  and  refraction  of  the  sun  on  that  particular  day  and  hour  be  known  to  the 
observer,  and  that  the  polar  axis  be  raised  precisely  to  the  co-latitude  of  the  place  of 
observation.  The  adjustments  are  few  and  simple,  and  need  to  be  verified  only  from 
time  to  time;  besides,  they  can  be  readily  verified,  being  similar  to  those  in  the  transit 
proper. 

Latitude  and  transit  observations  can  also  be  made  with  this  telescope  when  the 
sun's  altitude  is  too  high  for  observations  with  the  mam  telescope,  in  the  same  man- 
ner as  described  on  page  97  for  our  Interchangeable  Auxiliary  Telescope  style  1. 

This  solar  attachment  can  be  readily  attached  or  detached  from  the  transit  with- 
out altering  its  adjustments.  When  detached  the  transit  is  then  simply  an  ordinary 
complete  Engineers'  and  Surveyors'  Transit. 

By  the  use  of  our  Latitude  Level  t  (fastening  to  the  cross  axis  at  the  side  of  the 
vertical  circle,  see  cut)  not  requiring  a  reading  of  the  vertical  circle  for  every  setting 
of  the  polar  axis  for  latitude  except  once  in  a  day,  observations  can  be  made  repeatedly 
with  speed  and  accuracy.  Indeed,  with  the  declination  and  refraction  of  the  sun  pre- 
viously worked  out  for  the  various  hours  of  the  day,  observations  can  be  made  nearly 
as  fast  as  a  needle  of  the  surveyor's  compass  can  be  read.  A  concise  description  and 
use  of  both  attachments  will  be  found  in  the  Manual. 

The  weight  of  the  solar  attachment  and  top  telescope  combined  is  1  lb.,  with  coun- 
terpoise, 2  Ibs. ;  that  of  the  latitude  level  about  }4  lb.  Both  are  screwed  into  the  in- 
:ode  Words  strument  box. 

Manthus      Price  of  Solar  Attachment  with  Small  Telescope,  as 

generally  supplied  for  solar  work,  without  counterpoise,!  but 

with  prism  and  colored  glass,  $52.OO 

Hcentra        Price  of  Latitude  Level,  as  in  cut,  $15.OO 

*  Other  telescopic  solars  of  similar  design  as  heretofore  made  may  be  out  from  y%  to  }£"  from  the 
center  of  the  main  telescope,  and  then  of  course  there  must  be  a  divergence  of  the  lines  of  sight  of 
both  telescopes  involving  errors  to  that  amount. 

fThe  honor  of  first  conceiving  the  idea  of  applying  a  small  telescope  in  place  of  the  lens  bar  and 
of  using  a  spirit  level  for  the  accurate  setting  of  the  polar  axis,  belongs  to  Mr.  C.  L.  Berger,  of  this 
firm.  See  Catalogue  of  1878. 

JThis  latitude  level  can  also  be  used  for  grades  and  distance  measurements,  etc.  It  will  be  found 
to  form  a  very  useful  adjunct  to  the  Engineers'  Transit,  even  without  the  solar  attachment. 

§  It  is  not  strictly  necessary  to  counterpoise  the  smaller  solar  attachment  in  order  to  obtain  good 
work. 


173 


a 


The  Berber 
Solar  Attachment. 


A.  Instrument  with  Solar  Attachment  ready  for  an  observation. 

B.  Eye  end  view  of  Solar  Attachment  showing:  patent  lateral  adjustment  to  enable  us  to  place 
the  Solar  Telescope  exactly  In  the  same  vertical  plane  with  the  main  one. 

D.     Latitude  Level,  If  ordered,  for  use  with  Solar  Attachment, 
b,  b.     Wire  Diaphragrm  in  Solar  Telescope. 


174 


Davis'  Patent  Solar  Attachment. 

This  invention  is  destined  to  supersede  all  other  solar  attachments,  being  by  far 
the  most  accurate,  the  most  aimpU,  and  the  cheapest  in  use.  The  sun  observations  are 
made  with  the  instrument's  telescope  direct,  whereby  greater  range  and  power  are 
secured,  and  limiting  the  adjustments  to  those  common  to  the  instrument  proper 
itself.  It  can  be  attached  to  any  engineers'  and  surveyors'  transit  which  has  a  good 
vertical  arc  or  full  vertical  circle.  A  great  many  have  been  placed  on  our  transits 
(sizes  Nos.  1,  2,  3  and  occasionally  on  No.  4),  for  the  use  of  U.  S.  Deputy  Survey- 
ors, and  others  having  occasion  to  do  solar  work. 

However,  as  its  manipulation  involves  a  few  mathematical  calculations,  differing 
somewhat  from  ordinary  solar  attachments,  we  advise  our  patrons  to  carefully  read 
pages  81  and  82,  etc.,  of  manual,  where  a  full  description  will  be  found. 

The  screen,  shown  in  Fig.  2,  can  be  applied  with  erecting  and  inverting  tele- 
scopes. In  making  an  observation  with  an  erecting  telescope  the  full  aperture  of 
the  object  glass  is  utilized,  but  with  an  inverting  telescope  it  must  be  limited 
to  about  X  or  ^  inch  diameter  to  get  the  wires  sharply  defined  on  the  screen.  To 
this  end  the  telescope  cap  is  provided  with  a  central  opening,  permitting  of  such  an 
adjustment,  which  may  be  closed  entirely  when  not  in  use. 

Attachments  shown  in  Figs.  3  and  4  are  for  direct  observation  when  the  sun's 
altitude  does  not  require  the  screen.  These  latter  attachments  are  now  made  by  us 
in  a  manner  superior  to  those  shown  in  these  cuts  on  opposite  page.  They  are 
mounted  as  in  Fig.  5,  upon  a  frame,  readily  attachable  to  the  eye-piece  by  means  of 
a  clamp,  which  can  be  clamped  in  any  position  most  convenient  for  the  observer. 
To  bring  the  colored  glasses  or  the  prism  before  the  peep-hole  of  the  eye-piece,  it  is 
only  necessary  to  revolve  them,  hence  they  can  be  used  in  rapid  succession.  It  will 
be  seen  that  these  solar  attachments  are  easy  to  manipulate,  and  therefore  must 
insure  better  results  than  heretofore  obtainable  with  mechanical  devices  of  any 
other  kind. 

Price  of  Solar  Screen,  Figs.  1,  2  and  3 -16.00 

"        "  Plain  colored  glass,  Fig'.  4 2.00 

"        "       "         "  "     mounted  in  Shutter,  Fig.  C>,  when  ordered 

with  Transit 2.50 

"     Fig.   6  with  Eye  Piece  Cap,  when   subse- 
quently ordered      .         .  ...  3.00 

"       "     Prism  and  colored  glass,  Fig.  7 8.00 

'•        "  Prism  and  colored  glass,  improved  mounting,  Fig.  5          .         .  12.00 

u        "  Solar  Screen  with  improved  prism  and  colored  glasses  combined.  18.00 


Code-Daphne 


C.  L.  Berger  &  Sons'  Patent  Inclined  Square. 

For  Sun  Observations  with  Davis'  Patent  Solar  Attachment. 

This  device  consists  of  four  additional  wires  forming  an  inclined  square  of  equal  sides  placed  at  an  angle  of 
45°  with  the  usual  cross  wires,  and  equi-distant  from  the  latter's  point  of  intersection  in  the  Surveyor's  Transit 
Telescope.  The  space  contained  within  this  square,  as  will  be  seen  in  the  greatly  enlarged  Figures  g  and  £  a,  is 
slightly  smaller  than  the  sun's  disc ;  thus  an  observation  of  the  sun  for  position  can  be  made  by  simply  setting 
the  telescope  by  means  of  the  tangent  screws  until  the  four  segments,  formed  by  the  black  lines  against  the  bright 
disc  of  the  sun,  are  of  equal  size.  In  this  manner  the  sun's  disc  can  be  better  bisected,  as  when  it  must  be 
quartered  by  the  cross  lines  alone  —  but,  if  desired,  both  methods  can  be  applied  as  a  check  upon  each  other. 

The  arrangement  of  the  wires  in  the  inclined  square  is  in  no  way  confusing,  as  it  keeps  the  cross  and  stadia 
wires  distinctly  apart  for  the  regular  work  of  the  transit,  and,  in  rapid  work,  is  a  help  to  distinguish  the 
horizontal  from  the  stadia  wires,  as  shown  above,  which  cannot  be  said  of  the  erect  square  H  — also  patented,  — 
shown  on  the  page  illustrating  the  various  sighting  wire  diaphragms.  Part  T. 

Price  of  Patent  Inclined  Square,  but  only,  when  ordered  with  the  instrument,  extra     .        84.no 

also  provided  with  Stadia  Wires,  as  in  cut,  .  7.0O 

**  "  "        with  cross  and  stadia  wires  for  instruments  of  other  make         10.09 


175 

C.  1.  BERGEK  &  SONS. 


Fig.  2. 


Fig.l 


Fig.  3. 


Solar  Screen 
Daisy 


Davis*  Solar  Attachments, 


Fig.  4. 

Glass 

mounted  in 
Cap. 

Dandelion 


Attachable    to    any    of    our 
Transit  Eyepiece  Caps 


Fig.  6. 

Glass 

mounted  in 
Shutter. 

Daorma. 


Fig.  5. 
Dahlia. 


Plain  Prism 
with  colored  glass 

Attached  to  Eyepiece  Cap. 


Ber 


ger  Improved  Prism  and  colored  glass  attachment 

"  A  "  —Prism,  "  B  "  —  Peephole,  "  C  "  —Colored  Glasses. 


NOTE.  — 

A  diagonal   Eyepiece  cannot  be 
advantageously    attached    to    a 
mine  transit,  since  it  must  inter- 
change with  the  regular  eyepiece 
of  the  inverting  kind,  and  there- 
fore frequent  breaking  of  the  cross 
wires  from  dirt  and  water  would 
be  a  constant  source  of  annoy- 
ance, especially  in  dark  places.  Beside 
such   instruments    the  telescope    must  I 
pushed  considerably   farther   through 
axis  and  a  heavy  counterpoise  permanently 
attached  to  the  eye-end  of  barrel  to  balance 
the  telescope,  and  the  latter  will  then  only  reverse  at  eye- 
end  through  the  standards.  For  sights  inaccessible  to  the 
main  telescope  in  mine  work,  nothing  better  has  been 
introduced  than  our  interchangeable  auxiliary  telescope, 
described  later  on. 


Fig.  8. 

Diagonal  Eyepiece  with  Swivel  Adapter 

for  Zenith  Stellar  Observations 

applicable  only  to 
Inverting  telescopes  of 

Transit-Theodolites 


Zenith 


Price,  $20.00 


176 

THE  5|"  MOUNTAIN  TRANSIT. 

This  instrument  is  of  the  same  size  and  in  other  respects  similar  to  that  described 
under  Transit  size  No.  2,  but  being  intended  for  use  in  mountainous  regions, it  is  pro- 
vided with  an  extension  tripod  to  adapt  it  to  suddenly  changing  grades,  and  in  order 
to  facilitate  the  reading  of  the  verniers  without  stepping  aside  the  latter  are  placed  at 
an  angle  of  30°  to  line  of  sight.  This  transit  has  a  full  vertical  circle  protected  by 
an  aluminum  guard.  Its  work  is  as  accurate  as  that  of  larger  transits  of  its  class. 

Mountain  Transit  No.  2.  A's  in  cut  shown  on  opposite  page,  but  without 
Davis  Solar  Screen.  SPECIFICATIONS :- 


Horizontal  circle  5Hnch  (at  edge  of  graduation),  graduated  on  heavy  inlaid 
ring  of  solid  silver,  double  opposite  verniers  read  to  minutes,  two  rows  of 
figures  0  to  360  in  opposite  directions;  figures  inclined  in  the  direction  verniers 
should  be  read;  verniers  at  30°  to  line  of  sight. 

Vertical  circle  5-inch,  graduated  on  solid  silver,  double  verniers  read  to  minutes. 
Telescope  1  OX -inch,  objects  erect,*  aperture  1*4  inch,  power  18  dia. 
Stadia  wires,  fixed,  in  ratio  1:100. 

Spirit  level  5^ -inch,  with  clamp  and  tangent  screw  to  telescope. 
Plate  levels  of  standard  length  and  very  sensitive. 
Magnetic  needle  3%"   edge-bar  form  having  no  index  error. 
Shifting"  center,  to  set  instrument  exactly  over  a  given  point. 
Punch  mark  on  top  of  telescope,  to  enable  to  center  the  transit  from  a  point  above. 
Standards  leatherized  (see  page  9). 
Extension  tripod. 

The  Mahogany  case  has  a  leather  strap,  hooks,  etc.  It  contains  a  sun-shade,  a  wrench, 
a  screw-driver,  an  adjustable  plumb-bob,  a  magnifying  glass,  an  adjusting  pin,  and 
weighs  about  7  Ibs. 

Weight  of  transit  about  10  Ibs.  ;  weight  of  extension  tripod  from  9  to  11  ^  Ibs. 

Gross  weight  of  transit  packed  securely  for  shipment  in  two  boxes,  about  55  Ibs. 

Code  word  Forsythia.  Price,  $252.OO 

A  reduction  of  $15.OO  can  be  made  if  graduations  are  not  on  solid  silver. 

Extras  to  Mountain  Transit  No.  2. 

Gradienter  Attachment,     .....                   ....  $5.00 

Offsetting  arrangement,      ..........  5.00 

Variation  Plate,  adapted  for  all  declinations  E.  or  W 10.00 

Quick  leveling  attachment  (see  manual),            ......  15.00 

Full  length  split-leg  tripod,  for  use  with  transit  in  ordinary  practice  (see  Note)  16.50 

Plain  Prism,  t  with  colored  glass,  for  observing  the  sun's  altitude  (fig.  1),  8.00 

Improved  Prism,  with  colored  glasses,  for  observing  the  sun's  altitude  (fig.  5),  12.00 

Davis'  Solar  Attachments,  screen  with  improved  prism  mounting  (p.  175),  18.00 

Berger's  Solar  attachment  (pp.  172  and  173),    .  70.00 

"        Latitude  Level  attachment,         .......  15  00 

Short  Focus  Lens  Attachment  (see  pages  101,  203).     One  pair,    .         .         .  16.00 

Leather  Cover  over  case  arranged  to  be  strapped  to  the  saddle  of  a  horse,  13.00 

"            "         "         "  as  above  with  shoulder  straps,         ....  15.00 

Cravenettehood  (heavy,  gives  good  protection);  silk  (light,  not  waterproof ),  each  1.00 

Bottle  of  fine  watch  oil,  for  the  centers  of  transit,           .         .         .         .         .  0.35 

NOTE. —  Although  the  extension  tripod  is  very  slender  and  about  2  Ibs.  heavier  than  our  regular  tripod,  its 
superiority  for  mountain  work  is  very  apparent.  Still,  for  general  practice,  it  is  desirable  to  have  the  regular 
tripod,  giving  greater  steadiness  and  increased  accuracy.  It  will  be  advantageous  to  order  both  kinds. 

It  will  be  observed  that  in  the  cut  the  verniers  of  the  horizontal  circle  are  placed  at  an  angle  of  35°  to  the  line 
of  sight  as  in  our  Mining  Transits,  thus  adapting  the  instrument  to  the  work  in  a  mountainous  country.  On 
the  other  hand  this  change  in  the  position  of  the  verniers  requires  the  level  in  front  of  the  telescope  to  be 
carried  beyond  the  limit  of  the  plate  in  order  to  be  of  standard  length  and  character,  and  although  fully  pro- 
tected in  its  partially  exposed  position  from  injury,  by  an  improved  guard  surrounding  it,  it  is,  nevertheless, 
subject  to  slight  changes  in  adjustment,  as  when  compared  with  one  mounted  as  shown  in  Transit  No.  2,  where 
verniers  are  placed  at  90°  to  the  telescope.  In  all  cases  where  this  change  in  the  position  of  the  verniers  is  not 
deemed  of  sufficient  importance,  we  advise  to  order  our  Transit  No  2.  A  small  striding  level,  illustrated  in 
Transit  No.  Id,  can  also  be  placed  upon  the  telescope  axis  at  an  extra  cost  of  $15.00. 

*  An  Inverting  Telescope  of  1%"  aperture,  1O%  inches  long  and  with  a  power  of  23  dia. 

can  be  supplied  with  the  above  transit  in  place  of  the  regular  erecting  one  ;  t  n  >  additional  cost,  but  the 
instrument  must  be  made  to  order.     This  telescope  is  particularly  well  adapted  for  stadia  work. 

t  In  a  mountainous  country,  it  frequently  happens  that  a  transit  must  be  set  up  in  places  where  it  is  ex- 
tremely difficult  to  gjet  standing  room  to  take  both  back  and  fore-sights.  With  the  aid  of  a  prism,  attached  to 
the  eye-piece,  all  this  can  be  done  from  the  side  of  the  instrument. 


C.  L.  BEKGEK  &  SONS. 


in.  at  edge  of  graduation 


Patented. 


Mountain  Transit  No.  2. 

(Shown  with  Solar  Screen  Attachment.*) 

For  size,  weight,  particulars  and  extras  of  this  instrument  see  opposite  page. 
Code  Word  (without  screen),  Forsythia.  Price  $252.OO 

(For  code  words  for  Extras  and  changes  from  Forsythia, 
see  pages  C,  F  and  Gr  of  complete  code  at  back.) 


*  For  description  of  this  Solar  Attachment  see  page  81  of  the  Manual,  and  for  illus- 
tration and  prices  see  pages  174  and  175. 


178 

The  41"  Mountain  and  Mining:  Transit. 

.  For  those  desiring  a  Transit  smaller  than  the  5^"  Mountain  Transit  just  described 
and  illustrated  under  No.  2,  but  larger  than  our  Transit  No.  4  (pages  18*'  183)  we  fur- 
nish this  one  in  size  and  weight  between  the  two.  With  this  exception  the  instru- 
ment is  like  our  Transit  No.  4,  as  will  be  seen  by  comparing  the  cuts.  It  has  com- 
pound centers.  With  careful  use,  necessary  only  on  acount  -of  its  lightness,*  it  is 
capable  of  very  accurate  results.  Owing  to  the  short  focal  length  and  high  power  of 
the  telescope  we  strongly  recommend  the  inverting  kind,  although  an  erecting  one 
can  be  supplied  to  order.  Instrument  packed  to  stand  upright  in  carrying  case.° 

Transit  No.  4^ 

SPECIFICATIONS  :  — 

Horizontal  circle  4^-inch,  graduated  on  heavy  inlaid  ring  of  solid  silver,  double  opposite 
verniers  reading  to  minutes,  two  rows  of  figures  0  to  360  in  opposite  directions,  figures  in- 
clined in  the  direction  verniers  should  be  read,  verniers  at  35°  to  line  of  sight 
Vertical  circle  4-inch  graduated  on  solid  silver,  double  verniers  reading  to  minutes 
Telescope  7^-inch,  objects  inverting,  aperture  IVe  inch,  power  18  dia. 
Stadia  wires,  fixed,  in  ratio  1: 100. 

Spirit  level  4-inch,  with  clamp  and  tangent  screw  to  telescope. 
Plate  levels  both  of  standard  length  and  very  sensitive. 
Magnetic  needle  3-inch  edge-bar  form  having  no  index  error. 
Shifting  center,  to  set  instrument  exactly  over  a  given  point. 

Punch  mark  on  top  of  telescope,  to  enable  to  center  the  transit  from  a  point  above. 
Standards  leather  finish. 
Extension  tripod.* 

The  Mahogany  case  has  a  leather  strap,  hooks,  etc.     It  contains  a  sun-shade,  a  wrench,  a  screw- 
driver, an  adjustable  plumb-bob,  a  magnifying  glass,  an  adjusting  pin,  and  weighs  about  4  Ibs. 

Weight  of  transit  about  G*/2  Ibs. ;  weight  of  extension  tripod  about  9  Ibs. 

Gross  weight  of  transit  packed  securely  for  shipment  in  two  boxes,  about  50  Ibs. 

code  word    Genila.  Price,  $247.OO 


Extras  to  Transit  No.  4V2. 


$  5.OO 
10.00 
8.0O 
4.OO 
8.5O 

198       .        .  35.00 

98  45.OO 


Gradienter  attachment  

Variation  plate  to  set  off  all  declinations  E.  or  W 

Prism  and  colored  glass  (plain  form  only  permissible,  Fig  3,  page  175) 

Reflector  for  illuminating  the  cross  wires 

Short  focus  lens,  pages  101,  203,  one 

Edge  graduation  for  vertical  circle,  with  a  double  vernier  at  eye  end,  page 
Edge  graduation  for  vertical  circle,  with  double  opposite  verniers,  page  19i 
Patent  interchangeable  auxiliary  telescope,  style  I,  page  189  .  .  37.0O 

Berger  solar  attachment  with  small  telescope,  page  172 5/8.OO 

Split-leg  tripod  in  addition  to  extension  tripod  furnished  with  the  transit   ....  16.5O 

Bracket  in  box,  page  203 14.OO 

Trivets,  page  204 

Lateral  adjuster,  page  205 25.OO 

Leather  cover  with  shoulder  straps 1 3.0O 

"       without    "  "  11.00 

Hood  to  protect  transit  from  rain  and  dust l.OO 

Bottle  of  fine  watch  oil .35 


*  We  furnish  with  this  instrument  a  heavy  extension  tripod,  such  as  furnished  with  transit  size  No.  2» 
This  secures  to  the  transit  the  necessary  great  rigidity  and  stability.  However,  when  required,  we 
can  furnish  an  extension  tripod  weighing  7  Ibs.  only  (price  being  the  same),  in  place  of  the  9^4  lb. 
tripod,  or  in  addition  if  desired  for  special  purposes.  We  can  also  furnish  the  stiffer  split-leg  tripod 
weighing  only  7J-£  Ibs.  in  place  of  the  extension  tripod.  This  we  recommend  very  strongly  whenever 
applicable. 


179 

C.  I,.  BEKGEK  &  SONS. 


No. 

n.  at  edge  of  graduation). 


Complete 
Mountain  and  Mining  Transit. 

For  size  and  particulars  of  this  instrument,  as  well  as  for  Kxtras,  see  opposite  page. 

Code  word,  Genila.  Price,  $247.OO 


180 
C.  L,.  BERGER  &  SONS.  BOSTON 

4|"     MONITOR  TYPE      Transit. 

With  Compass.  Cylindrical  Pivots  to  telescope  axis.  Wye-  Bearings. 

This  Monitor  Type  transit  has  been  designed  to  meet  a  demand  for  a 
lighter  instrument  than  size  No.  5>^  Monitor  Transit. 

The  same  general  description  of  our  No.  5H  Monitor  Transit,  page  166,  ap- 
plies to  this  No.  4:}^  Type  with  the  exception  that  vernier  B  is  single,  which  en- 

ables US  to  place  an  unusually  long,  sensitive  and  fully  protected  front  plate  level  011 
this  small  transit  and  does  not  project  over  the  vernier  plate.  We  do  not  furnish  a 
double  B  vernier.  On  just  this  one  feature  alone  this  type  With  the  double  A 

vernier  and  the  single  B  vernier  is  destined  to  supersede  the  regular  types 
made,  as  it  lessens  the  tendency  toward  errors.  In  general  practice  a  reading:  on  a 

Berg'er  transit  is  at  once  accurate  and  sufficient.  However,  if  the  A  and  B  double 

verniers  are  wanted  we  advise  ordering  No.  4^  transit  on  page  179. 

The  outer  or  contra  clockwise  row  of  figures  on  the  horizontal  circle  and  the 
corresponding  figures  of  the  right  side  of  vernier  A  can  be  furnished  in  Red  but  will 
be  made  to  order  only,  see  cat.  page  41.  Instrument  stands  upright  in  carrying  case. 

Monitor  Transit  No.  4, 


SPECIFICATIONS  :  — 

Horizontal  circle  4%-inch,  graduated  on  heavy  ring  of  solid  silver.   A  vernier  is  double. 
B  vernier  Is  single  reading  to  minutes,  two  rows  of  figures  0  to  360  in  opposite  directions. 
Figures  inclined  in  the  directions  verniers  should  be  read  :  Verniers  at  35°  to  line  of  sight. 
Vertical  Arc  4-inch,  graduated  on  solid  silver,  double  verniers,    reading  to  minutes. 
Telescope  8-inch,  objects  erect,*  aperture  ll/&  inch,  power  19  diameter. 
Stadia  wires,  fixed,  in  ratio  1  :  10O. 

Spirit  level  4-inch  with  clamp  and  tangent  screw  to  telescope. 
Plate  levels  both  of  standard  length  and  very  sensitive. 
Magnetic  needle  2fi  inch  edge-bar  form  having  no  index  error. 
Shifting  center,  to  set  instrument  exactly  over  a  given  point. 

Punch  mark  on  top  of  telescope,  to  enable  to  center  the  transit  from  a  point  above. 
Transit  leather  finished. 
Extension  tripod.  t 

The  Mahogany  case  has  a  leather  strap,  hooks,  etc.    It  contains  a  sun-shade,  a  wrench,  a  screw- 
driver, an  adjustable  plumb-bob,  a  magnifying  glass,  an  adjusting  pin,  and  weighs  about  4  Ibs. 

Weight  of  transit  about  Q%  Ibs.  ;  \veight  of  extension  tripod  about  9  Ibs. 

Gross  weight  of  transit  packed  securely  for  shipment  in  two  boxes,  about  50  Ibs. 


Code  word  Geminol. 


Price  $1 


Monitor  Transit  No.  4V  as  above,  but  with  4"  full  Vertical 
circle  and  aluminum  guard  in  place  of  arc. 

Codeword  Genony. 


Price 


Extras  to  Transit  No. 

Gradienter  attachment  

Variation  plate  to  set  off  all  declinations  E.  or  W. 

Prism  and  colored  glass  (plain  form  only  permissible,  Fig.  7,  page  175) 

Reflector  for  illuminating  the  cross  wires 

Short  focug  lens,  pages  101,  203,  one 

Edge  graduation  for  vertical  circle,  with  a  double  vernier  at  eye  end,  page  198 

Edge  graduation  for  vertical  circle,  with  double  opposite  verniers,  page  198 

Patent  interchangeable  auxiliary  teles'cope,  style  I,  page  189 

Berger  solar  attachment  with  small  telescope,  page  172 

Split-leg  tripod  in  addition  to  extension  tripod  furnished  with  the  transit   . 

Bracket  in  box,  page  203 

Trivets,  page  204  .... 

Lateral  adjuster,  page  205      . 

Leather  cover  with  shoulder  straps 

without     " 

Hood  to  protect  transit  from  rain  and  dust 
,  Bottle  of  fine  watch  oil  . 


*   5.00 

10.00 

8.00 

4.00 

8.50 

35.00 

45.00 

37.0O 

58.00 

16.50 

14.00 

25.00 

13.00 

11.00 

1.00 

.35 


*An  Inverting  Telescope  of  l'/8"  aperture,  TtVa"  long,  power  18  dia.  can  be  supplied  with 
the  above  transit  in  place  of  the  regular  erecting  one  at  no  additional  cost.  This  telescope  is  partic- 
ularly well  adapted  for  stadia  work.  Made  to  order  only. 

t  We  furnish  with  this  instrument  a  heavy  extension  tripod,  such  as  furnished  with  transit  size  No.  2. 
This  secures  to  the  transit  the  necessary  great  rigidity  and  stability.  However,  when  required,  we 
can  furnish  an  extension  tripod  weighing  7  Ibs.  only  (price  being  the  same),  in  place  of  the  9M  lb. 
tripod,  or  in  addition  if  desired  for  special  purposes.  We  can  also  furnish  the  stiffer  split-leg  tripod 
weighing  only  7^4  Ibs.  in  place  of  the  extension  tripod.  This  we  recommend  very  strongly  whenever 
applicable. 


181 

C.  L.  BEKGER  &  SONS.  BOSTON 


NO. 

iii.  at  edge  of  graduation) 


No.  4^  Complete  Monitor  Type  Transit 

F«>r  size  and  particulars  of  this  instrument,  as  wi'H  as  for  Extras,  see  page  18O. 


Code  word,  Geniinol 


Price, 


$248.00 


Cylindrical  Pivots  to  telescope's  axis  running  in  tlie  improved  adjustable  Wye- 
Block  Bearing.  The  center  point  is  located  on  a  round  hub  on  the  telescope's  axis  to 
letter  distinguish  it  in  dark  places  when  centering  under  a  point  above  the  transit. 

The  Eye-Piece  Cap  is  large  in  diameter.  It  affords  a  protection  to  the  eye  of  the  ob- 
server in  a  glaring  sun.  It  has  been  combined  with  a  dust  guard  which  fully  protects 
the  Eye-Piece  focussing  slide. 

The  Front  Plate  Level  is  fully  protected.  Improved  Leveling  Head  with  dust  caps 
to  leveling  screws. 

To  avoid  mistakes  and  to  save  time  telegraph  Code  name. 


182 


The  4"  Mountain, 


Mining  and  Reconnoissance  Transit. 

The  smallest  Transit  made  by  us. 

The  CUt  represents  a  complete  transit  of  this  class,  in  every  respect  similar  to  our  En- 
gineers' and  Surveyors'  large  transits  No.  1  and  No.  2,  except  in  size  and  weight.      The 

verniers  of  the  horizontal  circle  are  placed  at  35°  to  line  of  sight,  unless  ordered  to  be 
at  90°,  when  the  transit  must  be  specially  made.  The  instrument  has  compound  centers 
and  is  as  carefully  made  as  the  larger  ones,  and  with  careful  use,  necessary  only  on  ac- 
count of  its  great  lightness,*  capable  of  very  accurate  results.  For  use  in  mines,  moun- 
tains and  for  explorers,  travelers  and  for  preliminary  work  of  all  kinds,  as  well  as  to 
fill  in  details,  it  is  especially  adapted.  Owing  to  the  small  size  of  telescope  and  high 
power,  we  supply  the  inverting  kind.  The  instrument  is  packed  lying  down. 

Transit  No.  4  SPECIPICATIONS:- 

Horizontal  circle  4-inch,  graduated  on  heavy  inlaid  ring  of  solid  silver,  double  opposite 
verniers  reading  to  minutes,  two  rows  of  figures  0  to  360  in  opposite  directions,  figures  in- 
clined in  the  direction  verniers  should  be  read,  verniers  at  35°  to  line  of  sight. 
Vertical  circle  4-inch  graduated  on  solid  silver,  double  verniers  reading  to  minutes. 
Telescope  7%-inch,  objects  inverting,  aperture  I'/s  inch,  power  18  dia. 
Stadia  wires,  fixed,  in  ratio  1:10U 

Spirit  level  4-inch,  with  clamp  and  tangent  screw  to  telescope. 
Plate  levels  both  of  standard  length  and  very  sensitive. 
Magnetic  needle  2%-inch  edge-bar  form  having  no  index  error. 
Shifting  center,  to  set  instrument  exactly  over  a  given  point. 

Punch  mark  on  top  of  telescope,  to  enable  to  center  the  transit  from  a  point  above. 
Standards  metal  finish. 
Extension  tripod.* 

The  Mahogany  case  has  a  leather  strap,  hooks,  etc.     It  contains  a  sun-shade,  a  wrench,  a  screw- 
driver, an  adjustable  plumb-bob,  a  magnifying  glass,  an  adjusting  pin,  and  weighs  about  4  Ibs. 

"Weight  of  transit  about  5  Ibs. ;  weight  of  extension  tripod  about  9  Ibs. 

Gross  weight  of  transit  packed  securely  for  shipment  in  two  boxes,  about  45  Ibs. 

Code  word  Genista.  Price,  $247.OO 

Mountain,  Mining  and  R.  Transit  No.  4,  as  above,  but 
with  arc  only  in  place  of  full  vertical  circle  and  guard. 
Code  word,  Galanthus.  Price,  $238.OO 


Extras  to  Transit  No.  4. 

Gradienter  attachment                 $  5.OO 

Variation  plate  to  set  off  all  declinations  E.  or  W 1O.OO 

Prism  and  colored  glass  (plain  form  only  permissible,  Fig.  7,  page  175)  8.OO 

Reflector  for  illuminating  the  cross  wires 4.OO 

Short  focus  lens,  pages  101,  203,  one 8.5O 

Edge  graduation  for  vertical  circle,  with  a  double  vernier  at  eye  end,  page  198       .        .  35.OO 

Edge  graduation  for  vertical  circle,  with  double  opposite  verniers,  page  198      .        .       .  45. OO 

Patent  interchangeable  auxiliary  telescope,  style  I,  page  189          .       .  STf.OO 

Berger  solar  attachment  with  small  telescope,  page  172 52.OO 

Split-leg  tripod  in  addition  to  extension  tripod  furnished  with  the  transit   ....  16.5O 

Bracket  in  box,  page  203 14.OO 

Trivets,  page  204 

Lateral  adjuster,  page  205 25.OO 

Leather  cover  with  shoulder  straps 12.5O 

"       without     "            "                          10-50 

Hood  to  protect  transit  from  rain  and  dust l.OO 

Bottle  of  fine  watch  oil  .               -35 


*  We  furnish  with  this  instrument  a  heavy  extension  tripod,  such  as  furnished  with  transit  size  No.  2. 
This  secures  to  the  transit  the  necessary  great  rigidity  and  stability.  However,  when  required,  we 
can  furnish  an  extension  tripod  weighing  7  Ibs.  only  (price  being  the  same),  in  place  of  the  9M  Ib. 
tripod,  or  in  addition  if  desired  for  special  purposes.  We  can  also  furnish  the  stiffer  split-leg  tripod 
weighing  only  73^  Ibs.  in  place  of  the  extension  tripod.  This  we  recommend  very  strongly  whenever 
ipplicable. 


appl 


183 
C.  L.  BERGER  &  SONS. 


No.  4 

(4  in.  at  edge  of  graduation.) 


Instrument 
Packed  Ikying  Down 


Complete 

Mountain,  Mining  and  Reconnoissance.  Transit. 

For  size  and  particulars  of  this  instrument,  as  well  as  for  Extras,  see  opposite  page. 

Code  word,  Genista.  Price,  as  above,  $247.OO 

(For  code  words  for  Extras  and  changes  from  Genista, 
see  pages  C,  F  and  G-  of  complete  code  at  back.) 


184 

The  4" 
Complete  Transit- Theodolite  No.  4b. 

With  Yoke  Standards  and  Wye-Bearings.     Without  Compass. 
Size  as  in  No.  4,  page  182. 

For  triangulatioii,  filling-  in  details,  etc.,  in  secondary  triangular 
tioii,  also  for  explorers,  engineers  and  surveyors  where  the  large  instruments 
described  under  No.  11,  etc.,  become  undesirable  on  account  of  their  size  and  weight. 

The  Yoke  Standard  frame  is  of  our  advanced  pattern,  cast  in  a  single  piece 
of  aluminum  *  (unless  ordered  to  be  of  brass  composition),  to  gain  great  lateral  stiff- 
ness, and  is  leatherized.  The  inverting  telescope  can  be  reversed  over  the  bearings  by 
turning  the  upper  covers  aside,  and  also  in  the  usual  way  through  the  standards.  The 
graduation  of  the  horizontal  circle  and  its  verniers  are  protected  by  glass. 

If  double  opposite  verniers  are  desired  for  the  vertical  circle  the  figures  will  then 
run  from  0-90-0  and  back  (as  in  the  regular  field  instruments),  instead  of  clockwise  with 
single  opposite  verniers  enumerated  below.  A  level  is  attached  to  the  vernier  arm 
(instead  of  to  the  telescope  as  in  Xo.  4).  This  instrument  will  be  made  with  three  lev- 
eling screws  only  and  packed  lying  down  in  its  carrying  case. 

Made  to  order  only. 

Complete  Transit-Theodolite  No.  4  b,  as  in  cut  on  opposite  page. 

SPECIFICATIONS:  — 

Horizontal  circle  4-iiicli  (at  edge  of  graduation),  graduated  on  heavy  inlaid 
ring  of  solid  silver,  single  opposite  verniers  read  to  minutes,  one  row  of  figures 
0  to  360;  verniers  at  90°  to  line  of  sight. 
Vertical  circle  4-iiich,  graduated  on  solid  silver,  single  opposite  verniers  read 

to  minutes,  one  row  of  figures  0-360  clockwise  (unless  ordered  otherwise). 
Compound  centers  of  bell  metal. 

Telescope  7^-illch,  Objects  inverting,  aperture  l1^  inch,  power  18dia. 
Stadia  wires,  fixed,  in  ratio  1 : 100 

Spirit  level  2^-indl,  with  reversible  clamp  and  tangent  screw  to  vernier  arm 
Striding"  level  rests  at  points  of  contact  in  wyes. 
Reading  glasses  to  horizontal  and  vertical  circles. 
Plate  levels  both  of  standard  length  and  very  sensitive. 
Shifting  center,  to  set  instrument  exactly  over  a  given  point. 
Punch  mark  on  top  of  telescope,  to  enable  to  center  the  transit  from  a  point  above. 
Standards  leatherized  (see  page  9). 
Extension  tripod. 

The  Mahogany  case  has  a  leather  strap,  hooks,  etc.  It  contains  a  sun-shade,  a  wrench 
a  screw-driver,  an  adjustable  plumb-bob,  a  magnifying  glass,  an  adjusting  pin,  and 
weighs  about  7  Ibs. 

Weight  of  transit  about  5  Ibs;  weight  of  extension  tripod  9  Ibs. 

Gross  weight  of  transit  packed  securely  for  shipment  in  two  boxes,  about  50  Ibs. 

Price  of  Small  Complete  Transit- Theodolite  No.  4b,  as  de- 
scribed above  and  shown  in  cut  (with  extra  vertical  wires  if  desired  forstellarob- 
servation) 

Codeword,  Gorastis.  $315.OO 

Extras  to  Transit  No.  4b. 

Compound  centers  made  of  steel  running  in  sockets  of  cast  iron  to  insure  freest  motion  with 

_  perfect  fit  .        . .  £20.00 

Spirit  level  4-inch  with  reversible  clamp  and  tangent  screw  to  telescope  (see  cut  No.  4.)  in  ad- 
ditions to  level  to  vernier  arm  shown  in  the  opposite  cut 12.OO 

Plain  prism  and  colored  glass  ( Fig.  7,  page  175) 8.OO 

Split-leg  tripod  in  addition  to  extension  tripod  (latter  furnished  with  transit)  .        .        .     16.5O 

"Leather  cover  with  shoulder  straps 12. 5O 

"  "      without     "  "  .         .  1O.5O 

Hood  to  protect  transit  from  rain  and  dust l.OO 

Bottle  of  watch  oil      .... .35 

*  If  desired,  the  U-shaped  standard  frame  can  be  made  of  brass,  weighing  about  1  Ib. 
more,  no  extra  charge.  If  instrument  is  to  be  used  near  salt  water,  brass  will  prove 
more  durable  for  this  standard  frame,  as  aluminum  and  its  alloys  are  apt  to  be  affected 
by  salt  water,  saline  and  alkaline  vapors  and  liquids. 


185 
MERGER  &  SONS, 


No.  4b. 

(4  in.  at  edge  of  graduation.) 


Small 
Complete  Transit- Theodolite  No.  4bo 

For  size  and  particulars  of  this  instrument,  as  well  as  for  extras,  see  opposite  page 

Code  word  Gorastis. 


For  code  words  for  Extras  and  changes  from  Gorastis 
see  pages  F,  O  and  H  of  complete  code  at  back.) 


Price,  as  above,  $315.OO 

Made  to  order  only. 


For  a  transit  of  a  similar  description  but  with  a  4^-iiieh  horizontal  circle, 


see  next  page, 


>Iade  to  order  only. 


186 

4>4  "  Complete  Mine  Transit  No.  4k. 

With  Yoke  Standards  and  Wye-Bearings.     Without  Compass. 

For  use  where  Transits  sizes  Xo.  2,  3  and  6  are  considered  too  heavy  and  No.  4  anrt  4b 

too  light  in  weight. 

The  Transit  shown  in  the  cut  on  opposite  page  is  best  fitted  for  underground  work 
on  account  of  its  fully  enclosed  vertical  circle.  However,  with  a  change  from  this  lat- 
ter type  to  any  of  our  open  forms  of  vertical  circle,  such  as  described  and  illustrated 
on  pages  155,  159,  193  and  200,  this  instrument  is  equally  well  adapted  for  engineer- 
ing and  surveying  work  of  all  kinds,  and  its  price  will  be  correspondingly  lower. 

The  Yoke  standard  frame  carrying  the  Wye-bearings,  combined  with  the  larger  hor- 
izontal circle,  is  of  a  type  permitting  of  the  placing  of  the  plate  levels  of  standard 
length  and  character,  in  a  manner  more  satisfactory  than  in  the  4-inch  Transit  No.  4 
described  and  illustrated  on  pages  182  and  183.  This  frame  is  of  aluminum,  and  being 
cast  in  a  single  piece,  gives  great  lateral  stiffness  to  the  telescope  and  its  attachments 
and  is  leatherized  or  japanned  as  we  deem  it  best.  If  desired,  this  frame  can  be  fur- 
nished in  brass,  when  the  weight  of  the  instrument  will  be  increased  about  one  pound. 
If  the  front  plate  level  is  desired  to  be  in  the  center  of  the  Yoke  standards,  as  shown 
in  the  cut  of  the  Engineers1  Transit  No.  1m,  then  the  height  of  the  Yoke  frame  is 
thereby  raised  ^-inch  and  the  external  shape  of  the  latter  will  be  like  that  illustrated 
in  No.  4  b  Transit.  The  telescope  reverses  through  the  standards  as  usual. 

Instead  of  three  level  ing"  screws,  this  instrument  can  have  four,  when  a  reduc- 
tion of  §10.00  will  be  made  from  the  price  given  below. 

Made  to  order  only. 

Complete  Mine   Transit  NO.  4k.    As  in  cut,  with  three  leveling  screws. 

SPECIFICATIONS :  — 

Horizontal  .circle  4%-inch  (at  edge  of  graduation),  graduated  on  heavy  inlaid  ring  of  solid 
silver;  double  opposite  verniers  read  to  minutes,  two  rows  of  figures 0  to  360  in  opposite  direc- 
tions; figures  inclined  in  the  direction  verniers  should  be  read,  verniers  at  30°  to  line  of  sight, 
glass  covered. 
Vertical  circle  4-inch,  fully  enclosed,  edge  graduation  on  solid  silver,  glass  covered, 

double  opposite  verniers  read  to  minutes,  figured  from  0-90-0  and  back. 
Detachable  reading  glasses  with  reflectors  for  horizontal  and  vertical  circles. 
Compound  centers  bell  metal. 

Telescope  iy2-incl\,  objects  inverted,  aperture  1%-inch,  poAver  18  dia. 
Stadia  wires,  fixed,  in  ratio  1 :  100. 

Spirit  level  4%-inch,  with  clamp  and  tangent  screw  to  telescope. 
Plate  levels  of  standard  length  and  very  sensitive. 
Gradienter  attachment. 

Shifting  center,  to  set  instrument  exactly  over  a  given  point. 

Punch  mark  on  top  of  telescope,  to  enable  to  center  the  transit  from  a  point  above. 
Illuminator  shade. 
Extension  tripod. 

Instrument  packed  to  stand  upright  in  carrying  case. 

The  mahogany  case  has  a  leather  strap,  hooks,  etc.     It  contains  a  sun -shade,  a  wrench,  a  screw- 
driver, an  adjustable  plumb-bob,  a  magnifying  glass,  an  adjusting  pin,  and  weighs  about  5  Ibs. 
Weight  of  transit  about  5  Ibs. ;  weight  of  tripod  about  9  Ibs, 
Gross  weight  of  transit  packed  securely  for  shipment  in  two  boxes,  about  45  Ibs. 

Code  word,  Grallus.  Price,  $336.OO 

This  transit  with  an  open  face  graduation  to  the  vertical  circle 

with  double  opposite  verniers  shown  on  page  155,  but  without  reading  glasses, 

Code  word,  Grumla.  Price,  $316.OO 

Extras  to  Transit  No.  4k. 

Center  of  steel  running  in  sockets  of  cast  iron,  insuring  freest  motion  with  perfect  fit  .         .  1818.0O 
Striding  level  resting  at  points  of  contact  in  wyes  as  in  No.  n  (applicable  only  when  there  is 

no  Style  I  interchangeable  telescope  ordered  for  this  instrument) 22.OO 

Iievel  and  spring  tangent  screw  to  vernier  frame  for  the  control  of  vertical  angles  as  in 

No.  4b,  in  place  of  the  level  to  the  telescope,  no  extra  charge. 

!Level  and  spring  tangent  screw  to  vernier  frame  in  addition  to  fixed  level  to  telescope,  1O.OO 

Solar  attachment  with  small  telescope  as  on  page  172  but  with  counterpoise        ....  52. OO 

Prism  and  colored  glass  (only  plain  form,  Fig.  7,  page  1 75,  permissible) 8.OO 

Short  focus  lens,  pages  101,  203,  one 8.5O 

Patent  interchangeable  auxiliary  telescope,  style  I,  page   189* 37  .OO 

Split-leg  tripod  in  addition  to  extension  tripod  furnished  with  the  transit 16.5O 

Bracket  in  box,  page   203 14.0O 

Trivets,  page  204  ....  

Lateral  adjuster  and  trivet  combined  for  three  leveling  screws;  page  205      ....  36.OO 

Leather  cover  with  shoulder  straps 13. OO 

•'              "        without  "            "                                                   11.OO 

Hood  to  protect  transit  from  rain  and  dust l.OO 

Bottle  of  fine  watch  oil «35 

*  The  post  to  which  the  auxiliary  telescope  attaches  to  the  main  telescope  is  shown  in  cut;  but  this  post  is 
not  furnished  with  instrument  unless  the  interchangeable  auxiliary  telescope  is  ordered  with  the  transit. 


187 
C.  L,.   BERGEK  &  SONS* 


No.  4k 

in.  at  edge  of  graduation). 


Patented. 


Complete  Mine  Transit,  No.  4k 

With  edge  graduation  and  fully  enclosed  vertical  circle. 

For  use  in  Mines  and  Tunnels. 

Also  for  Bridge  and  Topographic  work,  etc.,  when  provided  with  our  open  form 

vertical  circle. 

(Fora  front  view  of  this  instrument  see  colored  illustration    ) 

For  size,  weight,  particulars  and  extras  of  this  instrument,  see  opposite  page. 


Code  word,  Grallus. 

(For  code  words  for  Extras  to  Grallus, 

see  pages  F  and  H  of  complete  code  at  back.) 


Price,  $336.OO 


^  188 

t4 

Mining  Transits. 

All  of  the  foregoing  instruments,  particularly  Nos.  2,  4V£  and  49  we  recommend 
2       for.  general  underground  work.     (The  latter  instruments  chiefly  on  account  of  their 
grea'ter  portability  and  lightness.)     The  telescope  may  be  either  inverting  or  erect, 
and  may  have  a  prism  attachable  to  the  ordinary  erecting  or  inverting  eye-piece  to 
facilitate  sighting  in  inclined  shafts.     We  frequently  attach  to  the  cross-axis  a  side 
telescope,  swinging  free  of  the  plates,  of  nearly  the  same  length  and  power,  which  per- 
5       mits  of  vertical  sighting  up  or  down  a  shaft  (see  pp.  93  to  95).    We  also  furnish  at- 
^       tached  above  and  parpllel  with  the  line  of  sight  of  the  main  telescope  of  Nos.  4,  4!£, 
5  and  6,  another  one  of  shorter  length  and  lesser  power  mounted  on  a  central  pillar  cast 
on  to  the  cross-axis  of  the  main  telescope,  as  in  Style  I.     (See  interchangeable  auxil- 
S       iary  telescope,  pp.  189,  192,  193,  95  and  96.) 

This  latter  telescope,  which  of  necessity  is  of  lesser  power  as  compared  with  our 

35       regular  side  telescope,  will  in  most  cases  be  deemed  sufficient,  as  sights  in  mines  are 

short.    Its  power  varies  from  8  to  15  diameters,  according  as  the  telescope  is  erecting 

*  or  inverting.    We  are,  however,  prepared  to  mount  one  of  same  length  as  our  regular 
;J      side  telescope  in  cases  where  a  complete  revolution  of  cross-axis  is  not  required.    It 

*  will  be  seen  that  vertical  sighting  up  or  down  a  shaft  can  be  done  with  ease  and  accu- 
se     racy,  and  this  latest  device  has  nearly  all  the  advantages  of  a  telescope  mounted  on  in- 
S,      dined  standards  with  none  of  its  faults.     When  not  in  use  the  auxiliary  telescope  may 
%       be  removed  at  will  and  stored  in  the  box.    As  will  be  seen  by  reference  to  the  descrip- 
tion and  cuts  of  this  device,  pp.  95,  96,  and  189,  the  auxiliary  telescope  can  also  be 

Sc      readily  attached  to  the  end  of  the  cross-axis  of  our  Mining  Transits  Nos.  4,  41/£,  5 
A      and  O  when  it  becomes  a  side  telescope. 

The  ready  Intel-changeability  from  top  to  side  makes  the  auxiliary  telescope  one  of  the  most 
^3  desirable  additions  to  a  Mining  Transit. 

a  To  avoid  errors  in  reading  cardinal  points,  the  compass  ring  is  figured  from  0°  to  360°,  the  same 

as  the  horizontal  circle.  Mining  instruments  should  have  large  vernier  openings  to  admit  of  as  much 
"3  light  as  possible,  and  all  graduations  should  be  on  solid  silver.  For  the  illumination  of  the  cross- 
£  wires,  a  small  reflector  is  sometimes  placed  in  the  center  of  the  cross-axis  of  the  telescope  of  our 
?3  larger  instruments;  but  as  in  the  smaller  telescopes  much  light  is  being  cut  out  by  its  use,  we  prefer 

5  to  attach  a  reflector  shade  in  front  of  the  object  glass . 

No.  5.  Mining  Transit. — Dimensions  as  in  No.  1  (unusually  large  size); 
§  graduations  on  solid  silver;  verniers  reading  to  minutes  are  provided  with  ground  glass 
»  shades;  5-inch  full  vertical  circle  with  aluminum  guard;  spirit  level,  fixed  stadia  wires, 
j-  clamp  and  tangent  screws  to  telescope;  extension  tripod,  etc.  Price,  $26O.OO 

y  No.  6.     Mining  Transit.  —  Dimensions   as  in   No.   2    (customary  size); 

~j  graduations  on  solid  silver;  verniers  reading  to  minutes  are  provided  with  ground  glass 

«  shades;  5-inch  full  vertical  circle  with  aluminum  guard;  spirit  level,  fixed  stadia  wires, 

1  clamp  and  tangent  screw  to  telescope;  extension  tripod,  etc.  Price,  $26O.OO 

Extras  to  Mining  Transits  Nos.  4,  4!£,  5,  6  and  7 

6  Striding  level  (for  description  and  illustration,  see  pp.  156  and  211) $20.00 

*  Stadia  wires,  fixed                 3.00 

*  Disappearing  cross  and  stadia  wires  for  erecting  telescopes  (p.  190).    Patented        .         .         .  6.00 
iff        Gradienter  attachment  for  Nos.  5  and  6 

.         Five-inch  vertical  circle  provided  with  double  opposite  verniers  (see  p.  155)    ....         20.00 

2  Edge  graduation  for  vertical  circle  with  a  double  vernier  at  eye-end,  which  is  glass-covered, 

jS               as  in  cut  (p.  198) -        -         extra  35.00 

Edge  graduation  for  vertical  circle  with  double  opposite  verniers  (p.  198)                           extra  45.00 

•3  Patent  short  focus  lens  (pp.  103,  101).    No.  1,  $8.50;  No.  2,  $8.50;  Nos.  1  and  2    .         .         .  16.00 

'35  Reflector  for  illuminating  the  cross-wires 4.00 

fl  Aluminum  guard  to  vertical  circle     ....  4.00 

g  Prism,  attachable  to  eye-piece    .... 

*  Detachable  side  telescope  with  counterpoise  (pp.  189,  193) 

"           Patent  interchangeable  auxiliary  telescope.    Style  I,  described  on  p.  96  and  shown  on  p.  193  37.00 

53         Berger  Solar  attachment  with  small  telescope  (pp.  172-173)        .         .  52.00 

•<+         Arrangement  for  offsetting  at  right  angles  to  telescope 5.00 

.2        Quick  leveling  attachment  for  size  No.  4,  $20.00;  for  all  other  sizes 15.00 

g         Half-length  tripod 13.50 

Extra  extension  tripod 23.50 

"      split-leg  tripod  (see  note  to  No.  3) 

**•*         Plummet  lamp  (large  size)            .         .         .     .  .         .        . 10.00 

=2                "           "      (small  size) 8.00 

*i         Bracket  in  box,  with  strap,  auger,  and  lever  (Fig.  I,  on  p.  203) 15.00 

v®        Trivet  (see  p.  204) 

!>         Plumbing  device  for  carrying  a  line  down  a  shaft  (p.  191),  $3.00  each;  per  pair              .         .  6.00 

«         Patent  Lateral  Adjuster  (p.  191) 25.00 

"d        Large  plumb  bob,  weight  4  Ibs.,  for  use  in  shafts 7.50 

r9         Bottle  of  fine  watch  oil -35 

^        Silk  bag,  to  cover  transit 1.00 

fe         Leather  case  for  No.  4,  with  or  without  shoulder  straps 10.50  to  12.50 

"       "    No.  6,      "      "         "  13.00  to  15.00 


189 


Diaphragm  showing  ar- 
rangement of  wires  as  used 
with  our  mine  transits,  to 
distinguish  center  horizon- 
tal wire  from  stadia  wires, 
to  avoid  mistakes. 


Patented 


Complete  Mining  Transit, 
With  Style  1,  Interchangeable  Aux- 
iliary Telescope. 

Size  as  in  Nos.  5,  6,  and  7.  For  a  general  descrip- 
tion for  Style  I,  etc.,  see  pages  96-97.  For 
price  and  attachments,  page  188. 

NOTE.  — With  the  addition  of  the  interchangeable  auxil- 
iary telescope  as  an  aid  to  the  customary  mine  transits,  with 
main  telescope  in  the  center  of  the  instrument,  the  most  diffi- 
cult engineering  problems  in  undergiound  surveying  become 
at  once  very  simple  and -the  results  tbtained  are  as  accurate 
as  those  in  surface  work  —  with  its  aid  all  sights  in  the  verti- 
cal plane  are  possible  where  the  main  telescope  will  fail,  and 
the  vertical  and  horizontal  angles  can  be  measured  with- 
out an  offset  or  corrections  for  excentricity  caused  by  the 
distance  of  the  auxiliary  telescope  from  the  main  telescope. 
It  is  sufficient  to  remember,  ivhen  sights  become  inac- 
cessible through  the  main  telescope  -when  measuring  hori- 
zontal angles,  to  place  the  auxiliary  telescope  on  top,  and 
when  the  same  conditions  prevail  in  measuring  -vertical 
angles,  to  place  it  on  the  side. 

When  the  auxiliary  telescope  is  detached,  the  transit  is 
just  as  serviceable  for  surface  work  as  any  other. 

For  use  of  the  auxiliary  telescope  for  astronomical  ob- 
servations, see  page  97.  For  finding  meridian  with  its  aid 
and  the  use  of  the  solar,  see  page  71. 

All  our  transits  are  provided  with  a  fine  punch  mark  on  top  of  telescope  to  enable  to 
center  instrument  from  a  point  above  as  well  as  from  below . 


190 


The 

See  M 
Fig.  1. 


Berger  Patent  Mine  Tachymeter  Nos.  4,  41>£  and  6. 

With  Style  I  Patent  Interchangeable  Auxiliary  Telescope  (pages  97  and  193). 
ming  Transits,  sizes  4  and  6,  pages  97  and  193.     For  price  of  instrument  and  extras,  see  pages 

182  and  188. 


General  arrangement  of  instrument  showing  upright  post  for  auxiliary  telescope,  and  a 
reflector  attached  to  object-glass. 

Fig.  2.     Interchangeable  auxiliary  telescope;  Fig.  7  its  counterpoise. 

Fig.  3.  Auxiliary  telescope  at  side  when  measuring  vertical  angles',  also  for  making  latitude  observa- 
tions (see  page  97),  when  sun  is  too  high  for  observations  with  the  main  telescope. 

Fig.  4.  Auxiliary  telescope  attached  to  vertical  post  for  use  as  top  telescope  when  measuring  steep 
horizontal  angles  and  when  surface  or  meridian  lines  must  be  carried  down  a  shaft  wh^n 
objects  cannot  be  seen  by  main  telescope,  as  well  as  for  time  observations  when  sun  is  too 
high  for  observation  with  the  main  telescope. 

Fig.  5.  Side  telescope  placed  parallel  with  the  main  telescope  in  emergencies  by  means  of  the  strid- 
ing level:  also  showing  manner  of  centering  from  point  above. 

Fig.  6.     Patent  short  focus  lens  attached  to  main  telescope,  p.  100. 

Fig.  8.  Patent  Disappearing  cross  and  stadia  wires;  inclined  wires  indicating  center  for  stadia  wires, 
for  erecting  telescope,  p.  122.  Continuation  on  page  191. 


191 


Fig.  9. 


Leather  ease  with  shoulder  straps.     For 
prices  see  page  188. 


Fig.  12.  Plumbing  Device  A  and  B  for  carrying  a 
meridian  or  surface  line  down  a  shaft  by 
the  plumb-line  method.*  Fig.  14. 

Fig.  13.  Lateral  adjuster  attached  to  tripod  with 
transit  mounted  upon  it  for  ranging  tran- 
sit on  to  given  line.  For  description  and 
method  of  application  see  page  205. 

Fig.  14.  Shows  in  graphical  manner  the  method  of 
carrying  a  line  down  into  the  shaft  by 
means  of  the  plumbing  devices  and  lateral 
adjuster. 

*  For  valuable  suggestions  in  carrying  out  the 
perfection  of  this  device  we  are  indebted  to  Mr. 
G.  H.  Potter,  M.  E.,  of  Butte,  Mont. 


ftAN  OF  SHAFT  AT  COLLAR 


13 


VERTICAL  SECTION  THROUGH  SHAF1 
14 


The  Berber  Patent  Mine  Tachymeter. 


192 

Complete  Mining  Transit  No.  6D,  without  Compass. 

Shown  with  our  Patent  Interchangeable  Auxiliary  Telescope.  Style  I. 

(See  pages  95  and  96.) 

Responding  to  many  solicitations  to  make  for  mines  containing  magnetic  ore, 
or  an  electric  plant,  a  transit  similar  in  style  and  accuracy  to  our  No.  11  (see  page 
180),  we  have  designed  the  instrument  illustrated  on  opposite  page.     It  is  light, 
portable,  and  of  the  same  size  as  our  Nos.  4,  41/4,  2  and  6  transits;  but,  owing  to  the 
.    .  omission  of  the  compass,  the  standards  are  cast  in  a  single  piece,  affording  greater 

lateral  stiffness,  with  increased  capability  to  withstand  rough  treatment.  It  is, 
adapted  to  all  the  complex  conditions  prevailing  in  underground  work,  and  is  very 
simple  in  style  and  manipulation.  It  possesses  all  the  advantages,  as  regards 
accuracy  of  division,  highest  permissible  telescopic  power,  and  sensitive  spirit- 
levels  of  larger  instruments.  With  the  interchangeable  auxiliary  telescope  added 
for  use  in  steep  sighting,  either  on  top  or  on  the  side  of  the  main  telescope,  as 
required,  it  becomes  a  most  capable  instrument  for  correctly  solving  what  would 
otherwise  require  special  instruments  and  methods.  When  the  auxiliary  telescope 
is  detached,  it  is  just  as  applicable  to  the  common  work  in  the  mine  or  on  the 
surface  as  our  regular  engineers'  and  mining  transits  Nos.  4,  41/£,  2  and  6. 

The  U-shaped,  standard  frame  of  the  telescope  is  made  of  aluminum,  covered 
with  a  fine  dark  Japan  not  affected  by  moisture;   all  other  parts  are  finished  in  the 
same  manner  as  in  our  other  instruments.    The  plate-levels  are  of  our  standard  char- 
acter and  length,  mounted  directly  upon  the  upper  plate,  where  they  are  easily  acces- 
sible for  the  purpose  of  adjustment  and  ready  observation,  and  are  fully  protected 
from  falling  bodies.     The  principal  plate-level  is  directly  under  the  eye-end  of  the 
03  §"          telescope.    The  two  opposite  verniers  of  the  horizontal  circle  are  in  line  of  sight  with 
"3  So  the  telescope,  and  are  protected  from  dripping  water  by  cemented  glass  covers.    The 

circle  itself  is  provided  with  two  rows  of  figures  from  0°  to  360°,  in  opposite  direc- 
tions, with  double  verniers  to  correspond  to  them  (unless  otherwise  ordered).    The 
M  a  &          vertical  circle,  with  figures  from  0°  to  180°,  both  ways  from  zero,  has  a  double  ver- 
"2|^  nier,  to  enable  the  observer  to  read  angles  of  elevation  or  depression  with  equal 

S  <s  '*  facility,  and  is  provided  with  an  aluminum  protection  guard,  which  carries  the  vernier 

^  ~o  §  and  also  serves  to  readily  adjust  the  latter  to  zero.     Double  opposite  verniers  can 

-j   §  T3  oo  also  be  placed  on  the  vertical  circle,  when  the  figures  will  run  from  0°  to  90°  each  way 
•3   a  §  ef'o   and  back  to  zero.    The  transit  has  inverting  telescopes  (unless  otherwise  ordered).    A 
O  'g  c  '-3  j|   new  and  important  feature  of  the  instrument,  which  greatly  increases  its  value,  is  this : 
^       I  S+3   tne  ^ne  9^  collimation  of  the  main  telescope  is  adjusted  for  distant,  very  near,  and 
0  J   intermediate  distances,  by  means  of  our  recently  patented  device,  to  a  nicety  never 
•g  c'^'g   before  attained;   and  no  readjustment  for  near  distances  is  necessary  except  after  a 
£'-gji  "   severe  accident. 

g  £  n  ,2  The  Style  I  interchangeable  auxiliary  telescope  described  on  pages  95  and 

°  ~  96,  and  illustrated  on  opposite  page,  is  non-adjustable,  but  it  has  been  so  much  improved 
.-£  "5  If  g*  that  the  line  of  collimation  of  its  principal  wire,  which  is  the  vertical  one  when  used  as 
^  §•'-£  o  top  telescope,  and  becomes  the  horizontal  wire  when  used  as  a  side  telescope,  lies  so 
"3  •£  P  u-,  nearly  parallel  to  that  of  the  main  telescope  as  to  be  practically  correct  in  most  cases. 
-gja.g  °  Weight  of  Mining  Transit  No.  GD  .  11  Ibs. 

o>  53"  .c  5  "      auxiliary  telescope  and  counterpoise,  each  12  oz.     .  .        \% 

2^5  o^  "      extension  tripod  .       about   9 

c  O  &  i  "      instrument  in  mahogany  box,  with  plumb-bob,  sun-shade, 

M&I)^£H  reading-glass,  etc.,  etc.  .       about  22 

Gross  weight  of  instrument  complete,  packed  securely  for  shipment  in 
S>  2  boxes  .  .  .50 

^  §«  No.  6D.  Mining  Transit  without  Compass,  as  in  cut,  with  Style  I 
t  JS  §  Interchangeable  Auxiliary  Telescope.  Horizontal  and  vertical  circles,  5  inches;  solid 
°  S'is  rjl  silver  graduations  reading  to  minutes;  ground-glass  shades ;  5-inch  level  to  telescope: 
^  $  ^  1  2  plate-levels;  inverting  telescope,  10  inches  long  by  iM-inch  aperture;  (if  erecting, 
S  -g  a  £  9%  by  1 M  inches) ;  powers,  24  diameters;  inverting  auxiliary  telescope  Ql/2  by  1  inch 
5  »  8r§  aperture;  (if  erecting,  7  by  1  inch);  fixed  stadia  wires;  gradienter;  2  illumi- 
ISgJ*  nator  shades;  extension  tripod,  etc.  Price,  complete  as  above,  $327.OO 

^  -g  &&  Price,  with  double  opposite  verniers  to  vertical  circle,  extra,     $  5.00 

b/D.=                             "    prism  attachment  to  eye-piece  8.00 

g  o>                 it          it    qmck  leveling  attachment  10.00 

'3  g                 "       without  Style  I  auxiliary  telescope  less,         37.00 

"       with  one  illuminator  shade  only  for  main  telescope  4.00 

Our  Interchangeable  auxiliary  telescope,  being  of  the  most  substantial  construction 
and  character,  may  also  l>e  used  for  finding  meridian  and  latitude  when  direct 
observations  cannot  be  made  with  the  main  telescope.  See  page  97. 


Interchangeable 
Auxiliary  Telescope. 


Counterpoise. 


Complete  Mining  Transit,  No.  6  D, 

With  Patent  Interchangeable  Auxiliary  Telescope  (Style  I.) 


|S 

go      Complete  Wet-Mine  Transit  No.  6H,  without  Compass. 

For  sole  use  underground. 
Shown  with  our  Patent  Interchangeable  Auxiliary  Telescope,  Style  1. 

This  Transit  is  of  same  size  and  has  the  same  characteristic  features  described 
c  •  under  No.  6D,  pages  192-3,  with  this  difference,  however,  that  it  is  specially  de- 
signed to  meet  the  more  exacting  requirements  existing  in  wet  mines,  with  the  object 
of  fully  protecting  the  horizontal  and  vertical  circles  from  dripping  water,  and  also  to 
a  certain  extent  from  the  action  of  fumes  and  gases,  if  used  in  coal-mines.  To  this 
end  the  upper  surface  of  the  vernier  plate  of  the  horizontal  circle  is  slanting  down- 
ward, the  vernier  openings  are  raised  above  the  surface,  arid  special  channels  are  pro- 
vided so  that  the  water  will  run  off  immediately.  The  same  can  be  said  of  the  verti- 
.  •  cal  circle,  as  will  be  seen  in  the  illustration  on  opposite  page.  In  order  to  more  fully 
protect  the  main  plate  level  from  accidents,  and  to  facilitate  its  reading  from  either 
side  of  the  instrument  in  the  dark,  it  has  been  placed  just  below  the  telescope  in  the 
center  of  the  upper  plate,  and  is  fully  protected  by  a  guard.  The  yoke  standard 
frame  has  therefore  been  remodeled,  and  like  its  prototype  No.  6D,  page  193,  is  of 
our  most  advanced  design  in  this  line,  combining  lightness  with  strength,  beauty  and 
general  adaptation  to  poor  artificial  light.  The  verniers  are  so  placed  that  no  shadow 
•  •  can  fall  on  and  interfere  with  the  reading  of  them  in  a  faint  light.  The  yoke 
standard  frame,  as  well  as  the  casing  surrounding  the  vertical  circle  and  the  upper 
horizontal  plate,  is  leather  finished  —  mine  waters  and  acids  do  not  affect  it  (see 
page  9). 

Owing  to  the  limited  distance  between  the  standards  and  the  larger  space  occupied 

"  by  the  wholly  encased  vertical  circle,  no  stride  or  revolving  cross-level  can  be  applied 

§*  to  this  instrument.     The  plate  level  in  the  center,  however,  is  one  of  sufficient  length 

%  Q       and  sensitiveness  to  insure  a  full  control  of  the  motion  of  the  line  of  collimation  in 

m  %  §<       the  vertical  plane.    The  yoke  standard  frame  enables  to  read  steeper  vertical  angles 

55  •"  So        direct  with  the  main  telescope  alone,  thus  often  obviating  the  use  of  the  auxiliary 

£  Z?~*        telescope.     The  whole  instrument  is  of  sturdy  build,  and  therefore  will  withstand 

3  JS  -^        rough  treatment.    No  water  can  come  in  contact  with  the  vertical  circle  or  verniers 

^  'fi  £*       as  they  are  completely  enclosed  in  a  casing  resembling  a  disc  in  form,  thereby  allow- 

Q  i  -J2       ing  all  water  to  trickle  off  while  in  use,  but  when  the  instrument  is  carried  on  the 

^  "3  "3        tripod  or  in  hand  it  should  be  so  held  that  the  front  surface  of  the  vertical  circle 

®  §  i  ^  is  tilted  slightly  upward. 

^  2  TJ  ,*5  Owing  to  this  disc-casing  this  instrument  is  not  so  well  adapted  to  surface  work 
'cs  g  §  where  a  strong  wind  pressure  against  the  disc  would  produce  vibrations  of  the  instru- 
3  g  ^  ment  and  great  liability  to  be  blown  over.  However  to  meet  a  growing  demand  for  a 
£f'|  cs  transit  of  type  No.  6  H  for  surface  as  well  as  for  mine  work  — where  conditions  in 
"•g  3  ^  latter  are  more  favorable  —  we  can  attach  in  place  of  the  fully  enclosed  vertical  circle 
>  cf  8  anv  one  of  tne  other  open  frame  protected  vertical  circles,  see  pages  193  to  200. 

Made  to  order  only. 


gj 


%  Xo.  6H  Complete  Wet-Mine  Transit  without  Compass,  as  in  cut,  but 
o  having  only  one  double  vernier  to  vertical  circle  at  eye  end,  with  style  I.  interchange- 
a  able  Auxiliary  Telescope.  Horizontal  and  vertical  circles,  5  inches;  solid  silver  grad- 
o  nations  reading  to  minutes;  ground  glass  shades;  edge  graduation  for  vertical  circle 
£  fully  encased ;  5-inch  level  to  telescope;  2  plate-levels  ;  inverting  telescope,  10  inches 
^  long  by  H-rnch  aperture;  (if  erecting,  9|  by  1£  inches);  powers,  24  diameters;  in- 
3  verting  auxiliary  telescope,  6£  by  1  inch  aperture;  (if  erecting,  7  by  1  inch);  fixed 
..  stadia  wires;  gradienter;  2  illuminator  shades;  extension  tripod,  etc. 

*  Price,  complete  as  above,  $352.OO 
8 

ID  Price,  with  double  opposite  verniers  to  the  edge  graduations  of  the  vertical 

circle,  extra,    I  10.00 

®         <.<.         u     flat  glass  covered  graduation  to  vertical  circle  (in  place  of  edge 

graduation)  with  double  vernier  at  eye  end  as  shown  on  p.  199       350.00 

*  n         i      flat  glass  covered  graduation  to  vertical  circle  (in  place  of  edge 

graduation)  but  with  two  double  opposite  verniers,see  page  199      360.00 

«     without  style  I.  auxiliary  telescope  less,  37.00 

o         it          «t       style  I.  auxiliary  telescope  but  with  provision  for  same,    u  27.00 

&        n        with  one  illuminator  shade  only  for  main  telescope  4.00 

For  other  Extras  see  page  188. 

NOTE.— Our  Interchangeable  auxiliary  telescope,  being  of  the  most  substantial 
construction  and  character,  may  also  be  used  for  finding  meridian  and  latitude  when 
direct  observations  cannot  be  made  with  the  main  telescope.  See  page  97. 


11)5 


Complete  Wet-Mine  Transit.    No.  6H. 

For  Price  and  Description  see  page  194. 


196 

Different  Types  of  Vertical  Arcs  and  Circles 
for  Mine  Transits,  etc. 

The  regular  arcs  and  vertical  circles  shown  in  the  Engineer's  and  Surveyor's  Tran- 
sits No,  Ib,  page  153,  No.  If,  etc.,  commend  themselves  for  their  simplicity  of  style, 
accuracy  of  graduation  and  ease  of  reading.  The  latter 'feature  is  particularly  well 
attained  in  the  above  instruments  where  the  double  verniers  are  situated  between  the  legs  of  the 
standard,  where  they  are  well  protected  from  injury  and  can  be  read  simultaneously  with  the  level 
attached  below. 

In  mines  and  underground  work,  where  often  the  Transit  must  be  set  up  in  cramped  places 
and  on  stages  erected  in  shafts,  the  difficulty  of  reading  the  vertical  verniers  without  stepping  aside, 
or  without  shifting  the  horizontal  plate,  becomes  apparent.  To  improve  these  conditions  and  in 
order  to  obtain  compactness  the  vertical  arc  in  the  older  types  of  instruments,  used  extensively  in 
the  coal  mines  of  Pennsylvania,  is  permanently  screwed  to  the  side  of  the  standard.  It  is  of  larger 
diameter,  and  has  a  movable  vernier  arm.  In  other  types  the  verniers  are  placed  at  the  sides,  as 
exemplified  in  No.  6d,  page  193,  etc.,  or  the  graduations  are  placed  on  the  edge  of  the  vertical  cir- 
cle, which  latter  type  embodies,  however,  a  great  deal  of  mechanical  refinement. 

All  of  these  types  have  advantages  and  disadvantages,  and  therefore  should  be  chosen  simply 
with  a  view  to  attain  highest  efficiency  of  an  instrument  intended  for  special  work.  It  will  hardly 
be  commendable  to  put  the  most  refined  style  of  vertical  circle  (requiring  a  more  careful  treat- 
ment—  not  to  speak  of  its  attendant  greater  cost  to  make  and  keep  in  repair)  upon  an  instrument 
intended  for  the  more  ordinary  purposes,  while  in  changed  conditions  all  these  refinements  may 
become  necessary  to  obtain  maximum  efficiency  under  trying  circumstances. 

To  enable  to  make  the  proper  selection  for  the  various  instruments  the  different  styles  are 
given  below. 


The  Pennsylvania  Arc. 

This  arc  is  of  larger  diameter  than 
usual  but  is  not  strictly  of  high  accu- 
racy. It  differs  from  the  regular  arc 
in  that  it  is  permanently  screwed 
to  the  standard,  and  that  its  movable 
vernier  arm  can  be  readily  set  at  zero 
and  clamped  to  the  cross  axis  with  the 
telescope  in  any  position,  enabling  to( 
read  vertical  angles,  plus  or  minus 
from  the  horizontal  plane  to  about  50 
to  60°  as  well  as  to  read  also  vertical 
angles  between  any  two  points,  when 
by  clamping  the  vernier  arm  at  0  for 
first  point  and  then  pointing  the  tele- 
scope at  second  point  the  angle  can  be 
read  from  0  of  graduation. 

This  arc  can  be  attached,  without  extra  cost,  to  any  Transit  of  size  and  style  No. 
1  and  No.  2,  in  place  of  a  regular  arc  enumerated  with  instrument.  Made  to  order  only. 


Code  Word. 
Eleusine. 


Movable  Arc. 

(Patented.) 

This  is  an  improved  form  over 
the  Pennsylvania  arc  in  so  far  as  it 
is  of  more  accurate  design  though 
similar  in  manipulation.  The  arc 
is  screwed  to  a  hub  which  is  revolv- 
able  on  the  cross  axis  of  the  tele- 
scope and  is  so  arranged  that  the 

hub  can  bt  readily  clamped  with  

telescope  in  any  position  and  with- 

out  straining  the  arc.  During  non-use  the  arc  can  be  clamped  to  the  vernier  frame  and  therefore, 
unlike  the  regular  arc,  never  projects  above  the  standards  when  the  telescope  is  in  reversed  posi- 
tion. The  vernier  can  be  set  to  read  zero  by  means  of  a  tangent  screw. 

The  mechanical  arrangement  of  the  various  parts  of  this  device  is,  however,  more  complicated, 
as  will  be  seen  from  the  cut,  and  on  this  account  it  is  not  only  more  expensive  to  make  but  is  mon, 
liable  to  derangement  as  compared  with  the  Pennsylvania  arc  or  the  regular  arc  (page  153)  fixed 
to  the  cross  axis  of  telescope.  Made  to  Order  only. 

Price  extra  (above  price  enumerated  for  regular  arc) 


197 


Code  Word  —  Beaman.       •NbiiliiM.Ji          Price,  extra,  $3O.OO. 

Made  to  order  only. 

See  page  155. 


The  Beamaii  Stadia  Arc. 

By  means  of  this  stadia  arc  there  is  determined  rapidly  and  exactly  the  difference  in  elevation 
between  instrument  and  rod,  and  also  the  reduced  horizontal  distance  to  the  rod,  without  the 
measurement  of  an  angle  as  such;  without  the  use  of  either  a  vernier  or  a  table,  slide  rule  or  diagram, 
and  with  but  trifling  computation. 

Stadia  Arc.    The  Stadia  arc  carries  two  scales: 
V.    A  multiple  scale,  used  only  for  elevation  determinations. 
H.    A  reduction  scale,  used  only  to  reduce  inclined  stadia  readings  to  horizontal. 

Index.  Either  scale  is  read  by  reference  to  an  index  adjusted  to  read  the  zero  or  initial  point  of 
the  scales  when  the  telescope  is  level.  This  adjustment  is  carefully  made  by  us  and  should  remain 
fixed. 

Signs  Proved.  The  initial  graduation  of  multiple  scale  is  marked  50  instead  of  0,  so  that  it* 
direct  reading  will  indicate,  and  the  notes  afterward  prove,  the  sign  of  the  angular  value  thereby 
represented. 

To  obtain  desired  multiple,  therefore,  subtract  50  from  multiple  scale  reading  and  use  algebraic 
remainder;  e.g.,  if  scale  reads  56,  multiple  is  56— 50  = +6.  If  the  scale  reads  47,  multiple  is 47— 50  = —3. 

The  numeral  50  has  been  selected  arbitrarily  as  a  convenient  one  to  use. 

"Whole  Numbers.  A  unique  feature  of  the  use  of  the  multiple  scale  is  that  only  such  inclina- 
tions of  the  telescope  are  used  as  will  give  a  whole  number  scale  reading,  the  fractional  part  of  the 
elevation  being  more  quickly  and  accurately  determined  by  a  final  rod  reading. 

There  are  upwards  of  80  such  graduations  on  the  multiple  scale  (indicating  multiples  running  from 
+40  to  —40).  The  process  involves  setting  the  telescope  so  far  as  to  catch  one  of  these  even  divisions, 
thereby  obtaining  a  whole  number  as  a  multiple  and  an  easy  multiplication. 

Difference  in  Elevation  Between  Instrument  and  Rod. 

Find  such  a  whole  number  multiple  arc  setting  (e.g.,  55  or  42  set  opposite  index)  as  will  throw 
middle  stadia  wire  somewhere  on  rod,  it  does  not  matter  where.  The  arc  reading,  minus  50,  when 
multiplied  by  the  observed  stadia  distance  (in  feet  subtended)  will  give  the  exact  difference  in  eleva- 
tion to  that  height  on  rod  which  the  middle  stadia  wire  now  happens  to  cut.  This  height  on  rod  is 
noted  and  allowed  for  as  a  final  correction. 

Reduction  of  Observed  Distance  to  Horizontal. 

The  direct  reading  of  the  reduction  scale,  taken  at  the  same  pointing,  gives  the  percentage  of  cor- 
rection (always  subtractive)  necessary  to  reduce  observed  stadia  distance  to  true  horizontal  distance. 
This  scale  may  be  read  to  nearest  division  (per  cent)  or  by  estimation  to  any  subdivision  desired. 

Illustration — Suppose  the  observed  stadia  distance  to  be  6.40  (640  feet),  and  that  the  telescope 
is  afterward  inclined  so  that  multiple  scale  reads  33,  at  which  arc  setting  the  middle  stadia  wire  reads 
7.4  feet  on  rod.  The  multiple  then  is  33-50  =  -17,  and  the  computation  for  a  foresight  would 
be  6.40X  — 17  =  —108.8:  and  —108.8— 7.4  = —  116.2  feet  =  difference  in  elevation  between  instrument 
and  base  of  rod. 

At  above  setting  reduction  scale  would  read  3  or  3%.  Then  3%  of  640=19.2  feet,  and  840-19= 
621  feet=reduced  horizontal  distance. 

Difference  in  Elevation  When  Half  Wire  Interval  is  Used. 

If,  however,  the  half  wire  intercept  must  be  doubled  to  read  a  long  distance,  it  may  happen  that 
no  exact  arc  graduation  setting  can  be  found  which  will  throw  middle  wire  anywhere  on  rod.  Then, 
instead,  make  such  even  arc  setting  as  will  throw  lower  wire  anywhere  on  rod.  (Can  always  be  done 
if  middle  wire  misses  rod.)  To  height  on  rod  thus  cut  by  lower  wire,  add  half  wire  intercept  above, 
which  obviously  gives  height  of  middle  wire  on  an  imaginary  extended  rod.  Then  compute  as  usual. 

Illustration —  If  half  wire  interval  is  4.2,  the  full  distance  would  be  8.4  (840  feet).  If  multiple 
scale  reads  46  while  lower  wire  cuts  rod  at  9.2  feet  above  its  base,  the  computed  middle  wire  reading 
would  be  9.2+4.2  =  13.4  feet.  Then,  with  multiple  of  —4,  compute  as  previously  explained. 


:i98 

Edge  G-racl nation  for  Vertical  Circle 

Avith  One  Double  A'ernier  at 

Eye-End. 

In  the  Transits  for  underground  work  provided 
with  a  full  vertical  circle  it  is  often  desirable  to  read 
the  angles  from  the  eye-end  of  the  telescope,  to  en- 
able the  manipulator  "to  secure  all  his  observations 
without  stepping  aside.  The  .Edge  Graduation  shown 
here  is  in  principle  like  that  illustrated  on  Transit 
No.  Gd,  page  193.  The  graduation  is  on  the  edge, 
protected  by  an  aluminum  frame,  and  the  double  ver- 
nier at  eye-end  is  glass  covered.  The  graduation  is 
on  solid  silver  and  reads  to  minutes.  It  is  made  in 
a  most  substantial  manner.  In  case  of  an  accident 
the  cost  of  repairing  is  considerably  greater  than 
that  of  the  regular  vertical  circle.  Made  to  Order 
only. 

Price  of  Edge-Graduation,  as 
shown  in  cut,  with  double  ver- 
nier at  eye-end,  glass  covered, 
(extra  over  price  of  Transits 
Nos.  4,  «5  and  6,  enumerated 
with  regular  full  vertical  circle)  $35.OO 


Code  Word, 
Heliotrope. 


Price  extra  over  price  of  instru- 
ment No.  6d 


25.OO 


(Patented.) 


Code  Word, 

Edge  Graduation  l^k^ililBfi^B   F^^^F     Hepatica. 
for  Vertical  Circle 
\vith  Two  Double 
Opposite  Verniers 

This  Edge  Graduation 
is  like  that  described  im- 
mediately above,  but  has 
two  double  opposite  ver- 
niers reading  to  minutes, 
which  makes  it  in  prin- 
ciple like  Style  O,  page  155. 
Made  to  order  only. 

Price  of  Edge  Graduation,  with  two  double  opposite  verniers,  glass  cov- 
ered, (extra  over  price  of  Transits  Nos.  4,  5  and  6,  enumerated 
with  regular  full  vertical  circle) $45.OO 

Price  extra  for  No.  6d •     .        .        .        .       35.OO 


(Patented.) 


Berber  Reading  Glass  and 
Reflector  with  counter- 
poise, for  edge  graduation 

Price,  $1O.OO 

Same  for  double  opposite  ver- 
niers   14.0O 


Heralia. 
Hestana. 


The  Fully  Enclosed  Vertical  Circle  with  Edge  Graduation. 

For  Transits  used  only  in  Mines,  Tunnels,  etc. 
Applicable  to  Transits  No.  4,  5,  6D,  6H,  and  7. 

In    distinction 
fo     the     open 

frame  form  of 
the  p  r  o  te  c  t  e  d 
vertical  circle 
shown  in  the 
foregoing  illus- 
trations, designed 
to  offer  the  min- 
imum resistance 
of  the  exposed 

area  of  a  Transit  to  wind  pressure  and  to  pre- 
vent the  instrument  from  being  blown  over  in 
surface  surveying,  we  recommend,  where  a 
transit  is  used  only  underground,  the  fully 
enclosed  type  to  protect  its  graduations,  as 
in  the  horizontal  circle,  from  dripping  water, 
and  to  a  great  extent  also  from  fumes  and  gases  exist- 
ing in  mines.  The  vernier  frame  shown  in  this  cut  is 
therefore  so  constructed  that  it  forms  a  shell  without 
any  openings  except  those  for  the  glass-protected  ver- 
niers. Two  semi-discs,  which  can  be  easily  removed 
whenever  desirable,  fit  into  this  v  ernier  carrying  shell 
at  the  back,  thus  encasing  the  vertical  circle  completely, 
but  allowing  it  to  move  freely  with  the  telescope.  No  _ 
water  can  penetrate  inside  this  shell  at  any  time  while  in  use,  nor  when  carried  on  its  tripod  or  in  hand,  if 
caution  is  taken  to  carry  the  instrument  so  that  its  front  outside  surface  is  slightly  inclined  in  an  upward 
direction.  Made  to  order  only. 

Price  of  vertical  circle  with  edge  graduation,  as  in  cut,  reading  to 
minutes,  but  with  only  one  double  vernier  at  eye-end,  glass-covered 
—  extra  over  price  of  Transits  !N"o.  4,  5  and  G,  enumerated  with 


Code  WovdB 


regular  full  vertical  circle 
Price,  extra  over  price  of  Transit  No.  6D 


$35.OO    Hestard 
25.OO    Hestene 


Price  of  vertical  circle  with  edge  graduations  as  in  cut,  with  two 
double  opposite  verniers,  reading  to  minutes,  glass-covered  —  extra 
over  price  of  Transit  No.  4,  5  and  G,  enumerated  with  regular  full  ver- 
tical circle  

Price,  extra,  for  Transit  No.  GD 


45.OO    Hestite 
35.OO   Hestium 


The  Fully  Enclosed  Vertical  Circle  with  the  Customary 
Face  Graduation. 

For  Transits  used  only  in  Mines,  Tunnels,  etc. 
Attachable  to  Transits  Nos.  4,  5,  6,  6D,  6H  and  7 

In  this  type  the  regular  ver- 
tical circle  and  verniers  with 
a  flat  graduation  (pages  155 
and  193)  are  encased  in  a  shell, 
closed  at  the  back  by  semi- 
discs,  to  protect  their  gradua- 
tion, from  dripping  water, 
etc.  In  all  other  respects  the 
design  is  similar  to  that  de- 
scribed above  for  the  edge 

graduation:  verniers  are  glass-protected  and  read  t 
minutes;  glass  shades  if  desired  can  be  added.     - 
striding  level  to  rest  on  special  collars  between  stan- 
dards, can  be  attached  if  desired,  but  only  to  Nos.  1 
and  5  Transiis.  Made  to  order  only. 

Price  of  vertical  circle  with  a  flat  grad- 
uation as  in  cut,  but  with  only  one 
dou  b  le  vernier  at  eye-en  d ,  glass-covered, 
extra  over  price  of  Transits  Nos.  4, 
5,  G  and  7,  having  regular  full  vertical 
m circle  (see  page  196)  •  $3O.OO 
Price  extra  over  price  of  Transit 

No.GD   .        .        .        .        15.OO 


Patented. 


Hestmos 
Hestnia 


Price   of  vertical  circle  as  in  cut,  with 
two    double    opposite   verniers,    glass 

covered,  extra  over  price  of  Transits  Nos.  4,  5,  G  and  7,  having  regular 
full  vertical  circle, $4O.OO   Hestota 

Price  extra  for  Transit  No.  GD 25.OO   Hestra 


The  Open-Frame  Protected  Vertical  Circle  with  the  Customary 

Face  Graduation. 

For  Transits  used  in  Surface  and  Mine  Surveying. 
Attachable  to  Transits  sizes  No.  1,  2,  3,  4,  5,  6  and  7. 


The  aim  of  this  device,  which  is 
similar  to  that  of  our  glass-protected 
edge    graduation    with    open    frame, 
page    198,    is    to   place  the  same  re- 
finement, as  regards  protection  from 
dust  or  water,  upon  the  vertical  grad- 
uations, as  with  that  on  tho  horizontal  circle, 
when  such  is  desirable  for  the  highest  class 
of  work.  All  of  these  devices  tend  to  increase 
the  efficiency  and  life  of  a  graduation,  but 
at  the  same  time  complicate  an  instrument 
and  add  a  little  to  the  weight  c-f  the  upper 
part.  Made  to  order  only. 

Price  of  protected  vertical  circle 
with  open  frame,  as  in  cut,  but 
with  only  one  double  vernier  reading  to  minutes  at  eye-end,  glass-covered,  see 
Heliotrope  page  198,  —  extra  over  price  of  Transits  enumerated  with  full 
vertical  circle,  size  Nos.  1,  2,  4,  5  and  6 $3O.OO 

Price  extra  over  Mining  Transit  No.  6D 15.OO 

Price  of  protected  vertical  circle  as  in  cut,  with  tico  double  opposite  verniers,  glass- 
covered, — extra  over  price  of  transits  Nos.  1,  2,  4,  5,  6  and  7,  when  enum- 
erated with  a  regular  full  vertical  circle .  $4O.OO 

Price  of  protected  vertical  circle  with  open  frame     as    above,     extra     for    Transit 

No.  6D 25.OO 

Price  of  reading-glasses  if  desired  for  double  opposite  verniers,  extra  1O.OO 


Code  word* 
Hestula 

Hesmlil 


Hesudra 

Hesydo 
Hetarda 


The  Level  to  the  Vernier  Frame  of  Protected  Vertical  Circle. 


This  feature,  which  greatly  facili- 
tates the  reading  of  vertical  angles 
without  requiring  the  instrument  to 
be  leveled  up  accurately,  can  be  added 
to  any  of  the  foregoing  styles  of  pro- 
tected vertical  circles,  when  so  ordered 
with  instrument. 

As  will  be  seen,  the  level  is  placed  upon 
the  vernier  frame,  which  latter  has  a  spring 
tangent  screw  by  which  the  bubble  can  be 
readily  brought  to  the  center  of  its  tube. 
When  properly  adjusted  to  the  instrument, 
the  bubble  is  required  to  be  in  the  center 
when  the  zeros  of  verniers  and  vertical  circle 
are  in  coincidence,  and  when  the  telescope 
is  in  a  horizontal  position. 

Made  to  order  only. 

Price   of  level  w  ith  tangent  screw  attached  to  any  of  the  foregoing  protected  vertical 

circles,  extra $12.OO     Hetesy 


201 


Stride  Levels 

Resting  on  Special  Collars  between  the  Standards  (pages  148  and  149). 
If  desired,  a  stride  level  resting  on  special  collars  between  the  standards,  so  as  to 
revolve  with  the  telescope,  can  be  attached  to  Mine  Transits  Nos.  5  and  O  only,  if 
latter  are  not  to  be  provided  with  a  central  post  for  style  1  or  2  interchangeable 
auxiliary  telescope.  This  stride  level  cannot  be  attached  to  any  instrument  already 
made  —  such  Transits  must  be  specially  made.  Price  extra  $2O.OO 

If  a  stride  lev  el  of  the  above  kind  is  to  be  attached 
to  Mine  Transits  Nos.  5,  6  or  7,  having  style  1  or  2 
interchangeable  auxiliary  telescope,  then  the  arrange- 
ment of  the  central  post  and  stride  level  will  he  as 
shown  in  the  annexed  cut,  shown  also  on  page  209. 

Made  to  order  only. 

Price,  extra,  $3O.OO 

NOTE.  —A  stride  level  resting  on  special 
collars  cannot  be  attached  to  Transits  size 
Nos.  4,  6D  nor  OH. 

For  adjustment  of  this  stride  level  of  improved 
form,  see  page  56. 

Patented. 

The  Revolving  Cross-Level  for  Mine  Transits. 

This  is  a  very  ingenious  device  to  con- 
trol the  line  of  collimat'on  of  the  telescope 
at  any  altitude,  in  place  of  the  stride-level, 
but  owing  to  the  limited  distance  between 
the  standards,  and  the  short  distance  be- 
tween them  and  the  vertical  circle,  it  can  be 
applied  only  to  our  Mine  Transits  Nos.  5 
and  6;  or  to  No.  6D  if  latter  is  provided 
with  an  open  vertical  circle  of  style  shown 
on  page  193. 

Unlike  the  regular  detachable  stride- 
level,  this  cross-level  is  permanently  mounted 
upon  the  telescope's  axis  cf  revolution  by 
means  of  two  adjustable  uprights.  Its  advan- 
tages that  itis  revolvable  between  its  uprights, 
and  therefore  enables  to  watch  the  bubble 
in  very  steep  sighting.  We  recommend  it 
only  in  cases  where  a  regular  stride-level 
cannot  be  applied  owing  to  size  and  style 
of  instrument,  and  where  it  is  considered 
that  some  form  of  stride-level  is  a  necessary 
adjunct  to  a  Mine  Transit.  The  adjustment 
of  this  device  is  somewhat  more  compli- 
cated than  that  of  the  ordinary  stride-level  (in  comparison  with  which  it  is  also  ot  a  some- 
what minor  degree  of  accuracy),  but  by  the  aid  of  the  instructions  given  below  it  can  be 
made  at  any  time,  if  required.  Made  to  order  011iy. 


Patented. 


Code,  Hetica 


Price,  $35.OO 


Adjustment  of  the  Revolving-  Cross  Level. 

To  make  the  adjustment  of  the  revolving  cross  lei'el,  level  up  the  instrument  approximately,  place  its  supporting 
arms  vertical  and  bring  the  bubble  of  the  revolving  level  to  the  center  of  its  tube  by  the  instrument  leveling  screws, 
and  clamp  horizontal  plate.  Now  first  verify  the  lateral  adjustment  of  the  revolving  level  by  turning  it  on  its  axis 
some  20  to  30°  each  side  of  the  vertical.  If  this  adjustment  is  made  properly  the  bubble  will  stay  in  the  midd  e 
of  its  tube.  If  not,  make  it  so  (as  in  a  Wye  Level)  by  the  two  capstan-headed  screws  at  the  side  of  the  revolving 
level. 

Revolve  the  telescope  180°  on  its  cross  axis,  turn  the  revolving  level  face  up  again,  and  see  if  also  correct.  If 
not,  remove  half  the  error  by  the  vertical  capstan-headed  screws  of  the  revolving  level  tube  and  half  by  the  vertical 
capstan-headed  screws  of  the  supporting  arm  (this  latter  must  be  done  in  order  to  also  adjust  the  revolving  level 
simultaneously  to  the  telescope's  horizontal  axis  of  revolution)  and  then  repeat,  if  necessary. 

This  being  done,  place  the  supporting  arms  horizontal  and  also  make  the  adjustment  of  the  sup- 
porting am  at  90  degrees  to  the  former  adjustment  by  the  other  pair  of  capstan-headed  screws  of  the 
supporting  arm  and  then  revolve  the  telesco->e  180°  to  see  if  correct,  and  repeat  this  adjustment  if  necessary. 

These  adjustments  being  made,  it  is  well  to  repeat  all  of  them  in  the  above  succession  until  perfected.  When 
this  is  accomplished,  it  will  be  necessarv  to  make  the  adjustment  of  the  standard?,  so  that  the  telescope's  axis 
shall  be  truly  at  rieht  angles  to  the  vertical  axis  of  the  instrument:  in  other  words,  that  the  line  of  collimation  travel 
in  a  truly  vertical  plane.  This  can  be  done  and  verified  by  simplv  turning  the  instrument  180°  on  its  vertical 
center  and  removing  half  the  error,  if  anv.  by  the  leveling  screws  and  the  other  half  by  the  raising  or  lowering, 
as  the  case  mav  be,  of  the  vertical  adii'stine  srrews  provided  on  one  of  the  standards. 

On  the  whole,  it  is  a  somewhat  delicate  adjustment  to  make,  renuiring  some  patience,  and  is  best  performed 
on  a  window-sill.  When  properly  performed  it  is  just  as  likely  as  permanent  as  that  of  the  plate  or  a  stride-leveL 


202 

C.  L.  BEKGKK  &  SONS. 


Flexible  Jointed  Ann  with  Magnifier 

Attachable  to  Any  of  Our  Transits  for  Keadiiig  the  Vertical  and  Horizontal  Verniers 


Code  Word 


Price,  $7.5O 
Hetide 


The  Adjustable  Center 

On  Top  of  Transit  Telescopes  used  Underground!, 

Our  transits  are  made  mechanically  so  perfect 
that  the  fine  punch-mark  provided  on  top  of  the 
telescope,  to  enabl  to  center  the  instrument  from  a 
point  above,  is  seldom  more  than  one  to  two  hun- 
dredths  of  an  inch  from  the  true  center,  without 
any  other  device,  and  is  generally  considered  suffi- 
cient. But  for  cases  where  even  this  small  eccen- 
tricity is  objected  to, in  mine  and  tunnel  engineering 
of  a  very  precise  character,  we  have  devised  ac 
adjustable  center,  as  shown  in  cut,  to  be  attached 
to  the  post  (or  if  there  is  no  post,  to  the  top  of  the 
telescope's  axis,  if  same  has  been  originally  provided 
with  a  stud  to  receive  it  when  being  made)  by  means 
of  which  the  center  can  be  adjusted  to  be  correct,  enabling  to  set  up  the  instrument  undei 
a  given  point  so  that  the  prolongation  of  the  vertical  axis  of  revolution  of  the  transit  be 
truly  in  line  with  the  plumb-bob  hung  from  a  point  above,  thus  leaving  nothing  to  be 
desired. — This  operation  can  be  very  much  simplified  by  the  use  of  our  lateral  adjuster, 
see  page  205.— When  not  needed,  the  adjustable  center  can  be  unscrewed  and  screwed 
in  the  box.  If  a  top  telescope  is  to  be  used,  the  transit  proper  should  first  be  set  up 
correctly  under  the  given  point.  This  done,  the  adjustable  center  can  be  removed  and  the 
top  telescope  screwed  in  its  place.  This  device  once  properly  adjusted  to  its  transit  by  us 
does  not  require  any  more  attention  in  the  future,  unless  the  instrument  should  meet 
with  an  accident,  such  as  bending  of  the  standards,  or  of  the  telescope's  axis,  etc.,  when 
naturally,  after  it  has  been  repaired,  this  adjustment  of  the  centering  device  must  again 
be  made. 


Patented. 


Price  of  adjustable  center 
Code  word 


.    $3.5O 
.  HetiUo 


The  Berger  Bracket  for  Transit  or  Level. 

This  bracket  is  designed  for  supporting  the  instrument  under  conditions  when  the 
use  of  even  our  extension  tripod  is  inadmissible,  and  will  be  found  a  valuable  auxiliary 
for  mining  work.  The  instrument  can  be  screwed  upon  the  bracket,  as  on  a  tripod,  and 
the  transit  can  be  centred  above  or  below  a  given  point.  The  bracket  is  made  of  brass, 
so  fashioned  as  to  offer  the  greatest  rigidity,  and  is  furnished  with  an  auger  and  a  lever. 
Price,  One  bracket  made  for  Transit  No.  4,  with  four  leveling  screws  in 

box,  with  auger  and  lever "  $14.00 

One  bracket  made  for  Transit  No.  6,  as  above        .         .         .         .  15.00 

Every  additional  bracket  extra,  for  either  size        .         .         .         .  9.00 

Price  of  Bracket  as  above  (but  for  instruments  with  three  leveling 
screws  size  No.  5  and  6)  with  instrument  fastener  and  lateral  motion 
packed  complete  in  box  with  auger,  etc 26.00  Hilgrim 

Price  of  Bracket  for  transits  with  three  leveling  screws  size  No.  4  and 

4£  inch  24.00        Hilitos 

Short  Focus  Lens  Attachment.     (For  extended  description  see  page  100.) 

The  above  cut  of  our  wye  level  and  Fig.  II  illustrate  our  patented  Focus  Lens 
Attachment,  attachable  to  the  object  end  of  the  main  telescope,  which  permits  the 
focusing  of  objects  nearer  than  the  range  of  the  main  telescope  will  permit.  As  a  rule 
the  main  telescope  can  be  made  only  to  focus  objects  five  to  six  feet  distant  from 
instrument.  These  lenses  are  generally  furnished  in  pairs.  Lens  No.  1  will  permit 
focusing  of  objects  about  4  feet  from  instrument.  Lens  No.  2  will  permit  focusing  of 
objects  about  2 A-  feet  from  instrument ;  used  together  they  permit  focusing  of  objects 
about  two  feet  from  instrument. 

The  lenses  are  adjustable  to  the  line  of  collimation  of  the  main  telescope  and  per- 
mit of  a  high  degree  of  accuracy.  They  will  often  prove  of  great  convenience  as  an 
auxiliary  to  view  objects  that  are  too  near  for  observing  without  them.  Attachable 
to  transits  Nos.  1,  2,  3,  4,  5,  6,  and  to  our  wye  and  dumpy  level. 

Price.  Lens  No.   1 $8.50 

«     2  .  8.50 

*'         Lenses "     1  and  No.  2  ...        16.00 


204 


Style  of  trivets  used  with  transits  and  levels  having 
four  leveling  screws.  (Also  for  use  with  lateral 
adjusters,  see  page  205.) 


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205 


Patented. 

The  Berger  Lateral  Adjuster 

For  Transits  with  FOUR  leveling  screws.* 
For  use  on  tripods  aiicl  trivets. 

The  Lateral  Adjuster  shown  above  is  an  attachment,  made  of  brass,  separate  from 
the  Engineers'  Transit  and  its  tripod.  It  screws  to  the  tripod  and  then  the  instrument 
is  screwed  on  top  of  it.  It  is  designed  to  range  the  line  of  sight  of  a  Transit  after 
it  has  been  leveled  up,  quickly  and  accurately  onto  a  given  line  which  may  be  indi- 
cated by  the  plumbing  wires  A  and  B  in  a  shaft,  as  shown  in  a  graphical  manner  on 
page  191,  or  onto  a  line  given  by  any  two  station  points  in  a  tunnel  or  in  surface 
work,  without  disturbing  the  position  of  the  level  bubbles. 

Being  primarily  intended  for  underground  work  the  indicator  wheel  of  the  feed 
screw  may  serve  as  an  aid  in  moving  the  instrument  a  required  distance  in  the  dark 
in  ratio  of  hundredths  and  thousandths  of  a  foot. 

TO  OPERATE  THE  LATERAL  ADJUSTER.  —  Screw  it  firmly  to  the  tripod 
and  also  attach  Transit  to  it.  Place  both  index  marks  of  the  Lateral  Adjuster  in 
coincidence,  and  also  place  Transit  about  in  the  center  of  its  shifting  motion.  Then 
place  tripod  firmly  on  the  ground  in  such  a  manner  that  the  longitudinal  axis  of  the 
Lateral  Adjuster  is  approximately  at  right  angles  to  the  line  given  by  the  plumbing 
wires  A  and  B,  and  at  the  same  time  that  the  line  of  sight  shall  be  as  nearly  in  line 
with  these  wires  as  possible.  Now  level  up  carefully  and  move  the  line  of  sight  of  teles- 
cope on  to  wires  A  and  B  by  the  feed  screw  of  the  Lateral  Adjuster  until  the  inter- 
section of  the  cross-wires  of  the  telescope  and  both  plumbing  wires  are  contained  in 
the  same  vertical  plane.  When  Trivets  and  Lateral  Adjusters  are  ordered  for  old 
instruments  the  serial  number  must  be  given. 


Lateral  Adjuster  for  transit  No.  4  with  four  leveling 

screws,  see  large  cut  above 

This  lateral  adjuster  provided  with  detachable  trivet 

Topadil,  see  page  204 2  Ibs. 

This  lateral  adjuster  provided  with  detachable  trivet 
Topalate 

Lateral  Adjuster  for  transits  No.  1,  2,  3,5,  6  and  11, 

see  large  cut  above 

This  lateral  adjuster  provided  with  detachable  trivet 

Topana,  see  page  204 , 

This  lateral  adjuster  provided  with  detachable  trivet 

Topalis 4  Ibs.  7 

This  lateral  adjuster  provided  with  detachable  trivet 

Topaxset  6  Ibs. 

This  lateral  adjuster  provided  with  detachable  trivet 
Topazula 8  Ibs.  7  oz. 

Lateral  Adjuster  and  Trivet  Combined  f  see  small  cut 
above  —  for  transits  Nos.  1,  2,  3,  5,  6  and  11 
(when  latter  is  provided  with  four  leveling  screws.). .  4  Ibs.  5  oz. 

Lateral  Adjuster  and  Trivet  Combined,  same  as  To- 
pixdil  but  with  an  adapter  for  use  with  transit 
No.4  

Lateral  Adjuster  and  Trivet  Combined,!  same  as  To- 
pixdil  but  with  instrument  fastener  for  transits 
Nos.  1,  2,  3,  4,  5,  6  and  11  with  three*  leveling 
screws  . . . 


1    Weight 

Price 

Code  Name! 

S 
li  Ibs. 

$25.00 

Topexura 

t 

.   2  Ibs. 

30.00 

Topibus 

.  4^  Ibs. 

31.50 

Topicomus 

9 

.   2  Ibs.  7  oz. 

f 

25.00 

Topilera 

.  4  Ibs.  7oz. 

*• 

31.50 

Topimot 

4  11)G  7  07 

qi    Kf) 

Topiris 

t 

.  6  Ibs. 
£ 

O  L  .*J\J 

33.00 

Topisine 

.  8  Ibs.  7  oz. 
t 

33.75 

Topitel 

I 

•  4  Ibs.  5  oz. 

30.00 

Topixdil 

t 

411,0      K  n~ 

qq  on 

Topodillo 

1  OS.  O  OZ  . 

8 
g 

K  1-1.  „ 

Oo,Ov/ 
qc  nn 

•     O  IDS. 

OD.UU 

Topogony 

*  For  transits  with  three  leveling  screws,  see  Tunnel  Tripod  with  centering  and  aligning  de- 
vice, page  210. 

tThis  device  is  to  be  placed  upon  the  regular  tripod  head  of  our  transits  Nos.  1,  2,  3,  5,  6 
and  11,  when  these  are  ordered  to  be  provided  with  THREE  leveling  screws,  or  it  may  be 
used  independently  on  a  bracket.  As  will  be  seen  above  there  is  also  provided  on  top  the  instru- 
ment thread  for  attaching  transits  Nos.  1,  2,  3,  5,  6  and  11  having  four  leveling  screws,  so  that  all 
the  above  styles  and  sizes  of  instruments  having  either  three  or  four  leveling  screws  may  be  used 
interchangeably  on  this  three-screw  tripod.  It  is  of  great  advantage  when  a  variety  of  instru- 
ments are  to  be  used  on  the  same  work. 


200 


Patented. 


The  Lateral  Adjuster  screwed  to  a  Trivet 
For  Transits  with  FOUR  leveling  screws. 

For  use  in  Tunnels  and  Underground  Work  of  all 

kinds;   also  useful  in  tlie  erection  of  long 

Bridges,    Factories     and    their 

machinery  equipment,  etc. 

For  Prices  and   Particulars  of  tliese  auxiliaries- 
see  pages  2O4  and  2O5. 


207 


The  Berger  Tunnel  Tripod 


Patented 


\vitli  Centering:  ami  Aligning  Device  for  moving  Transit  with  three  leveling  screws 
under  ov  above  a  given  point  or  onto  a  given  line  —  see  cut  of  No.  1O  b. 

The  above  tripod  has  been  designed  to  facilitate  the  placing  of  our  Transits  with  three 
leveling  screws  in  the  axis  of  a  tunnel  or  onto  a  given  line  of  sight.  1-or  this  reason,  in  addition 
to  our  centering  device,  a  lateral  motion  lias  been  provided,  which  allows  the  Transit  to  be  moved 
with  ease  and  precision  and  without  disturbing  the  position  of  the  level  bubbles  mentioned  in  de- 
scribing the  Lateral  Adjuster  for  transits  with  FOUR  leveling  screws,  page  205. 

This  centering  and  aligning  device  is  very  simple  to  manipulate,  but  increases  the  weight  of 
the  tripod-head,  particularly  when  the  latter  is  wholly  made  of  brass  Thus  the  tripod-head  for  si/e 
No.  1  and  No.  11  Transits  is  heavier  by  about  2%  to  3  Ibs.,  that  for  No.  2  about  2  to  2%  Ibs.,  and 
for  No.  4  about  \l/2  to  2  Ibs.,  and  in  the  case  of  No.  1O  and  12  about  5  Ibs. 

TO  USE.  — First  place  the  uppermost  triangular  shifting  piece,  upon  which  the  instrument 
rests,  in  the  center  of  its  motion,  which  is  indicated  by  equal  spaces  all  around  it,  and  also  place 
the  lateral  adjuster,  which  is  the  lower  slide,  in  the  center  of  its  range,  indicated  by  two  small 
projections  on  the  tripod  head  and  S!OAV  motion  piece  of  the  lateral  adjuster. 

Then  place  the  tripod  head  in  such  a  position  that  the  motion  of  the  Lateral  Adjuster  is 
about  at  right  angles  to  the  line  of  sight;  after  which  level  up,  and  center  over  or  below  the  given 
point;  then  clamp  the  large  winged  central  nut  in  the  usual  manner  and  apply  a  slight  pressure 
by  turning  milled  headed  nut  which  acts  against  the  spring  of  the  instrument  fastener.  The  in- 
strument is  now  ready  for  angle  work. 

TO  USE  THE  LATERAL  ADJUSTER  FOR  ALIGNMENT.  —  Clamp  the  milled 
headed  screAV  on  top,  bearing  in  mind  that,  in  order  to  enable  the  feed  screw  to  move  the  instru- 
ment during  this  lateral  motion,  loth  the  large  iringed  central  clamping  nut  on  top  of  tripod  and  fastener 
spring  below  must  first,  be  released. 

'Inasmuch  as  the  pitch  of  the  feed  screw  corresponds  to  tenths  of  a  foot,  each  motion  of  a 
tooth  of  the  star  indicating  wheel  corresponds  to  a  thousandth  of  a  foot.  Thus  it  will  be  seen  that 
if  the  pointing  of  the  telescope  on  a  distant  scale  requires  the  instrument  to  be  moved  I/ 1000th  or 
5/1000ths  of  a  foot,  as  the  case  may  be,  that  the  manipulator  turns  1  or  5  teeth  around  the  index 
mark  and  the  object  will  be  attained.  When  the  line  of  sight  of  the  telescope  is  in  the  given  line 
in  the  tunnel  then  slightly  clamp  the  large  winged  central  clamping  nut  on  toi>  of  tripod  and  a^ain  slightly 
apply  the  .spring  of  the  instrument  fastener. 

If  in  the  course  of  operations  the  line  of  sight  must  be  moved  laterally,  then  the  central 
clamping  nut  and  spring  nut  must  again  be  first  slightly  released  from  the  shifting  piece  before 
any  lateral  motion  should  be  attempted. 

To  use  the  tripod  head  as  a  trivet,  unscrew  the  extension  legs  and  screw  the  three  4-inch  iron 
legs  in  the  places  assigned  them.  It  can  then  be  used  on  brackets  or  any  other  special  device 
rigged  up  to  receive  it  in  the  axis  of  the  tunnel. 

To  obviate  the  removing  of  the  legs  so  that  attachment  can  he  used  as  a  trivet,  a  special 
tripod  head,  having  centering  and  lateral  adjuster  devices,  but  without  wooden  legs,  may  be  or- 
dered. This  extra  head  complete  would  have  the  three  4-inch  iron  legs  heretofore  mentioned. 

After  the  Lateral  Adjuster  has  been  used,  before  putting  it  away,  it  will  be  well  to  clean  it, 
placing  the  triangular  shifting  piece,  as  well  as  the  lower  slow  motion  slide  of  the  Lateral  Ad- 
juster, again  in  a  normal  position,  and  then  clamp  both  by  the  central  clamping  nut  and  small 
knurled  nut. 

The  tripod  is  made  with  fine  mechanical  nicety  and  should  be  well  taken  care  of  in  order  to 
preserve  it  in  good  condition. 

This  device  (for  instruments  with  THREE  leveling  screws  only)  is  made  in  four  sizes  as 
follows  :  — 

For  Transits  No.  1,  5  and  11,       ....  Code  Name  Topoltuni 

"    Transits  No.  2,  3  and  (>,....  "        "  Topomara 

"   Transit    No.  4 "  Toponia 

"   Transits  No.  1O  and  12 Toposmus 

The  price  of  this  lateral  adjuster  over  the  regular  centering  device  furnished  with  our  tran- 
sit tripods  will  be  given  upon  application. 


Mining  Transit. 
Interchangeable  with  Lamp  Targets  above  Leveling  Screws. 

Telescope  is  mounted  on  standards  as  shown  in  cut  of  No.  3,  with  a  double  vernier 
between  the  legs  of  the  standard,  and  is  provided  with  a  striding  level,  see  cut,  page  156. 
Compass  Needle  33/i  inch. 

The  leading  feature  possessed  by  this  instrument,  as  made  by  us,  is  that  it  can  be  interchanged 
with  the  lamp  targets  above  the  leveling  screws  (see  opposite  page)  so  that  after  they  have  been  set 
up  their  relative  position  as  to  height  and  location  will  remain  exactly  the  same  upon  being  trans- 
ferred from  one  tripod  to  another.  It  is  an  instrument  especially  adapted  to  the  work  of  an  engineer 
in  mines,  and  as  such  involves  a  great  deal  of  apparatus  not  possessed  by  instruments  intended  for 
surface  work.  Two  lamp  targets  are  commonly  supplied  with  an  instrument  of  this  kind,  but  fre- 
quently one  only  is  ordered,  according'  to  the  character  of  the  work  for  which  it  is  intended.  The 
vertical  centers  of  the  lamp  targets  have  to  be  well  fitted  into  the  sockets  of  the  leveling  heads,  and 
in  consequence  they  cannot  be  furnished  separately.  The  engineer  will  therefore  decide  whether  one 
or  two  lamp  targets  are  necessary  for  this  work.  The  lamp  targets  are  of  the  same  height  as  the 
transit  measured  from  the  base  above  the  leveling  screws  to  the  line  of  sight,  and  each  is  provided 
with  two  spirit  levels.  The  targets  can  be  revolved  in  the  vertical  and  horizontal  planes.  By  means 
of  a  tubular  sight,  situated  on  top  of  the  target,  the  latter  can  be  readily  set  in  the  direction  of  the 
instrument  so  that  its  face  will  lie  at  right  angles  to  the  line  of  sight.  The  lamps  can  be  raised  or 
lowered  at  will,  and  can  be  detached  whenever  necessary.  It  is  of  the  bull's-eye  pattern,  and  the 
best  lard-oil  only  should  be  burned  in  it.  A  disc  of  milk-glass  placed  between  it  and  the  target 
furnishes  an  illuminated  background,  against  which  the  intersection  and  outlines  of  the  target  are 
seen  sharply  denned.  Made  to  order  Qnly> 

Weight  of  Mining  Transit  No.  7,  about 11     Ibs. 

one  lamp,  £    " 

Mahogany  box  containing  instrument  and  one  lamp,  target,  etc.,  about  32      " 
one  Extension  Tripod,  about  9 J  Ibs.;  two  Tripods,  "      19      " 

Gross  weight  of  instrument,  complete,  packed  securely  for  shipment  in  2  boxes,  about  70  Ibs. 

§  |  «  [  Weight  of  Mahogany  box,  containing  instrument  only,  about     .       .       .       .   22    Ibs. 

S-aJ  "  "  "  2  lamps,  targets,  etc.,       "        ....   26      " 

|5§1  "  three  Tripods,  "         .        ...   28*    " 

alt      \  Gross  weight  of  instrument,  complete,  packed  securely  for  shipment  in  3  boxes,  about  120  Ibs. 

No.  7  Mining  Transit,  size  as  in  Transit  No.  6,  but  with  one  lamp 
target  as  shown  on  opposite  page;  graduations  on  solid  silver;  verniers  reading  to 
minutes  are  provided  with  ground-glass  shades;  5-inch  full  vertical  circle;  aluminum 
guard;  spirit  level,  clamp  and  gradienter  screw  to  telescope;  illuminator  shade; 
striding  level  and  fixed  stadia  wires,  telescope  mounted  as  shown  on  page  156,  2  ex- 
tension tripods,  2  plumb  bobs,  etc.  Lamp  target  packed  in  instrument-box. 

Price,  $38O.OO 

No.  7a.  Mining  Transit,  as  above,  but  with  2  lamp  targets,  both  packed  in 
separate  box,  3  extension  tripods,  3  plumb  bobs,  etc.  Price,  $4GO.OO 


Mining  Transit  No.  7b.  with  Yoke  Standards. 

No.  7b.  Mining  Transit,  as  shown  hi  cut,  with  yoke  standards,  compass 
with  2^-inch  needle;  5-inch  fully  protected  vertical  circle  with  face  graduation; 
double  opposite  verniers  reading  to  minutes,  glass  covered;  interchangeable  auxiliary 
telescope,  Style  I;  striding  level;  stadia  wires;  illuminator  shade;  gradienter;  ad- 
justable center  for  accurately  centering  instrument  from  a  point  above;  one  lamp 
target  packed  with  instrument  in  one  box;  two  extension  tripods;  two  plumb  bobs. 
Weight,  size,  etc.,  as  above  in  Transit  No.  7.  Price,  $492.OO 

No.  7b.  Mining  Transit,  as  above,  but  with  two  lamp  targets  both  packed  in 
separate  box,  three  extension  tripods,  three  plumb  bobs,  etc.  Price,  $  572.OO 

For  price  of  extra  attachments,  see  Extras  to  Mining  Transits,  page  188. 

NOTE. —  To  interchange  the  instrument  and  the  lamp  target  proceed  as  follows:  —  First  withdraw 
the  spring  bolt  of  the  lower  clamp  for  the  outer  center  by  means  of  the  small  milled-headed  nut  at  the 
end  of  the  clamp  opposite  the  tangent-screw.  Then  loosen  the  clamp  screw  immediately  above  the 
leveling  head.  Now  upon  pulling  back  the  spring  bolt,  situated  at  the  side  of  the  clamp,  the  instru- 
ment or  the  lamp  can  be  detached  by  lifting  it  out  of  the  socket  in  the  leveling  head.  These  sockets 
as  well  as  the  clamps,  which  serve  to  fasten  the  instrument  or  lamp  target  to  the  leveling  head, 
should  be  kept  free  from  dirt  or  grit.  After  clamping  the  instrument  to  the  leveling  head,  to  pre- 
vent any  motion  in  its  socket,  and  then  releasing  the  small  milled-headed  nut  from  its  fastening  on  the 
spring  bolt  of  the  lower  tangent-screw,  the  transit  is  ready  for  work  and  can  be  manipulated  the 
same  as  other  instruments  of  our  construction. 

For  adjustment  of  the  transverse  striding  level,  see  page  56. 


209 

Mining  Transit  interchangeable  with  Lamp  Targets 
above  Leveling  Screws. 


Lamp  Targets  for  Transits  No.  7  and  No.  7b. 


Mining  Transit  No.  7b. 

With  Yoke  Standards. 
As  made  by  C.  L..  Berger  &  Song. 


Patented. 


210 

Tunnel  Transits. 

Xo.  1C  a  Tunnel  Transit  with  four  leveling  screws  and  without  lateral 
adjuster,  otherwise  as  enumerated  below  and  shown  on  opposite  page. 

SPECIFICATION :  — 

Horizontal  circle  6^-inch,  graduated  on  solid  silver,  double  opposite  verniers  reading  to  2O", 

two  rows  of  figures  from  0°-3GO°. 
Telescope  12-inch  inverting,  aperture  1%-inch,  power  28  dia.,  telescope  reversible  over  the  bearings 

as  well  as  through  the  standard  frame,  reversible  clamp  and  tangent  screw. 
Spirit  level  to  telescope,  6-iiich. 
Striding  level  resting  on  special  collars,  3%-inch. 
Stadia  wires  tixed. 
Reflector. 
Shifting  center. 
Standard  frame  of  aluminium  or  brass,  latter  preferred  on  account  of  its  greater  resistance  to 

gases  and  fumes. 
Kxtension  tripod  Made  to  order  only. 

Code  word,  Mobaco.  Price,  $292 


No.  lOb.  Tunnel  Transit  as  in  cut,  with  three  leveling  screws  ;  tunnel  tripod 
with  centering  and  aligning  device. 

SPECIFICATION  :  — 

Horizontal  circle  6^-inch,  graduated  on  solid  silver,  double  opposite  verniers  reading  to  2O", 

two  rows  of  figures  from  0°-360°. 
Telescope  12-inch  inverting,  aperture  1%-inch,  power  28  dia.,  telescope  reversible  over  the  bearings 

as  well  as  through  the  standard  frame,  reversible  clamp  and  tangent  screw. 
Spirit  level  to  telescope,  6-inch. 
Striding  level  resting  on  special  collars,  4%-inch. 
Stadia  wires  fixed. 
Reflector. 
Shifting  center. 
Standard  frame  of  aluminum. 
Extension  tripod.  Made  to  order  only. 

Code  word  Mobalis.  Price,  $342 


No.  lOc  Tunnel  Transit  as  in  cut  on  opposite  page  and  as  described  in  No. 
1Gb,  but  having  an  extension  tripod  with  shifting"  center  only  as  shown 
in  No.  llf. 

Made  to  order  only. 

Code  word,  Mobatony.  Price,  $3O7 


Extras  to  Tunnel  Transit  No.  1C  a  and  No.  lOb. 

Lateral  adjuster  for  transit  No.  10  a  with  four  leveling  screws  .         .        -$25.00 

7-inch  horizontal  circle,  double  opposite  verniers  reading  to  10  sec.,*  extra.          30.00 
5-inch  full  vertical  circle,  solid  silver  graduation,  double  opposite  verniers 

reading  to  minutes,  as  in  cut,  page  214         .......  50.00 

Reading  glasses  to  horizontal  circle ,  15.00 

Striding  level  resting  at  points  of  contact  in  Y's  (instead  of  resting  on  spe- 
cial collars  as  in  cut) extra         .  10.00 

Aperture,  1^-inch  instead  of  lf£-inch,  length  of  telescope  12  or  13^  inch 

long,  powers  respectively  28  or  34  dia.  .....  .10.00 

Gradienter  attachment          .........  5.00 

Steel  center  running  in  cast-iron  socket       .  20.00 

Extra  extension  tripod,  with  shifting  center  only,  for  transit  having  3  level- 
ing screws      .............  32.50 

*  Detachable  reading  glasses  should  always  be  ordered  for  a  10  «ec.  graduation. 
For  additional  Extras  to  Tunnel  Transits,  see  Extras  to  Mining  Transits. 


No.  lOb 
Tunnel  Transit 

With  three  leveling  screws  mounted  011  tunnel  tripod  with  Shifting  Center  and 
Aligning  Device.    See  page  2O7. 


For  Price  and  description  of  the  above  instrument,  as  well  as  list  of  extras, 

see  preceding  page. 
Codeword  — Mobalis. 


212 

Triaiigulatioii  Transit-  Theodolites. 

For  use  in  Cities  and  in  Bridge  and  Tunnel  Construction,  etc. 

Since  the  introduction  by  us  in  1875  of  this  style  Transit  with  Yoke  standard  frame 
cast  in  one  piece  and  mounted  directly  on  the  top  flange  of  the  inner  center,  the  de- 
mand for  them  in  all  lines  of  engineering  requiring  high  accuracy  lias  attained  so  great 
a  magnitude,  on  account  of  their  excellence,  as  could  not  be  foreseen  at  that  time. 
Many  of  these  instruments  are  in  use  in  the  survey  and  triangulation  of  our  largest 
cities,  and  are  giving  great  satisfaction.  Many  also  have  been  supplied  to  Colleges  and 
are  in  use  in  State  and  Boundary  Line  surveys. 

The  great  lateral  stiffness  attained  by  this  form  of  standard  frame  enables  to  make 
the  trunnions  of  the  telescope's  axis  cylindrical  and  to  mount  them  in  wye-bearings, 
thereby  securing  to  the  telescope  the  most  .accurate  movement  in  the  vertical  p»lane 
known.  The  telescope  reverses  through  the  standards  as  usual  and  over  the  bearings. 
The  trunnions  are  protected  by  dust-caps,  and  wherever  possible  capstan-headed 
screws  will  take  up  any  looseness  between  these  dust-caps  and  the  trunnions. 

These  Transit-Theodolites  are  made  with  three  or  four  leveling  screws. 

No.  11.  Plain  Transit-Theodolite,  with  four  leveling  screws,  as  in  cut, 
on  opposite  page,  but  without  level,  clamp  and  tangent  screw,  vertical  arc,  or  strid- 
ing level  to  telescope ;  in  all  other  respects  as  in  cut  of  No.  1  Ic.  Specifications : 
horizontal  circle  6  finches,  single  opposite  verniers,  as  in  fig.  5  page  38,  read- 
ing to  2O",  glass  protected  graduation  and  verniers,  one  row  of  figures  0  to  360 
clockwise  ;  12-inch  inverting'  telescope,  aperture  1^  inch,  power  28  diameters, 
achromatic  eyepiece  ;  telescope  is  reversible  over  the  bearings,  as  well  as  through 
the  standards  ;  long  compound  centers  of  hard  bell-metal ;  shifting  center  ;  split- 
leg  tripod;  aluminum  standard  frame  —  leather-finished;  mahogany  box  with 

screw-driver,  reading  glass,  adjusting  pins,  etc. 

Made  to  order  only. 

Code  word,  Mobax 

If  instrument  is  desired  with  an  erecting  telescope  of  24  diameters,  add  to  code 
word  "erect." 

\Veight  of  instrument,  about  14  Ibs.     Weight  of  tripod,  about  10  Ibs. 
Gross  weight  packed  in  two  boxes,  ready  for  shipment,  about  60  Ibs. 

Price  of  Plain  Transit-Theodolite  No.  11,  as  above,  with  four 

leveling  screws $225.OO 

Extras  to  Plain  Transit- Theodolite  No.  11. 

Three  leveling  screAvs   with  shifting:  center  (see  page  52)  .  .  -  .15.00 

7-inch  horizontal  circle  reading  to  10"  by  single  opposite  verniers,  single 

row  of  figures  0°  to  360°  clockwise 30.00 

Heading;  glasses  to  horizontal  circle  (should  always  be  ordered  with  instru- 
ment reading  to  10") 15.00 

Reversible  clamp  and  tangent  screw  to    telescope,    but  without    level  to 

latter 15.00 

6-inch  spirit  level  with  reversible  clamp  and  tangent  screw  to  telescope         .  30.00 
3-inch  striding  level,  as  in  cut,  to  rest  on  special  collars  to  revolve  through 

the  standards 20.00 

5-inch  striding  level  resting   at  points  of  contact  in  wyes,  see  page  214        .  30.00 

5-inch  vertical  arc,  as  in  cut  on  opposite  page   .......  20.00 

5-inch  full  vertical  circle,  (as  in  cut  page  214)  but  with  only  one  double 

vernier  reading  to  minutes  at  eye-end  ;  reversible  tangent  screw        .         .  45.00 
5-inch  vertical  circle,  see  cut  page  214,  double  opposite  verniers  reading 

to  minutes,  reversible  tangent  screw     ........  50.00 

3-inch  level  to  vernier  frame  of  vertical  circle,  see  cut  page  214      .         .         .  8.00 
Two  reading  glasses  to  vertical  circle,  see  cut  page  214               .         .                  =10.00 

Stadia  wires,  fixed,  ratio  1:100    ....                                                   .  3.00 

Gradi enter   screw  .  .  .  .  .  .  .  .  .  „  .  5.00 

Center  of  instrument  of  steel  running  in  a  socket  of  cast  iron,  for  instrument 

with  three  leveling  screws,  having  no  compass 20.00 

Oblong  compass  mounted  on  vernier  plate  at  side  of  standard,  with  motion  for 
setting  off  the  variation  (three-inch  needle  reads  only  a  few  degrees  each  way 
from  zero)  [For  instruments  with  bell-metal  centers  only]  ....«,  .  15.00 


213 


No.  11C,  Complete  Transit-Theodolite  with  four  leveling  screws,  (size 
and  particulars  as  described  in  Plain  Transit-Theodolite  No.  1 1 )  but  with  level, 
clamp,  and  tangent  screw,  5-inch  vertical  arc,  striding-  level,  and 
fixed  stadia  wires  to  telescope,  as  shown  above. 

Made  to  order  only. 

Code  word,  Mobaya.  Price,  $3OO 

For  Extras  see  list  of  Extras  to  Transit-Theodolite  No.  11. 


214 


No.  lib. 


Complete  Double  Opposite  Vernier  Attachment  to  5-incb  Vertical 

Circle,  with  Level,  Reading  Glasses  and  reversible 

Tangent  Screw  to  vernier  frame. 

Attachable  to  Plain  Transit-Theodolites  No.  11,  page  212  and  lid. 

NOTE. —  The  telescope  in  the  above  cut  has  no  level  attached  to  it,  as  is  frequently  the  case  in 
these  instruments,  and  in  consequence  the  vernier  frame  of  vertical  circle  carries  a  3-inch  level  by 
which  a  complete  control  of  the  position  of  its  verniers  is  assured  when  vertical  angles  are  measured. 

For  price  and  particulars  see  Extras  to  Plain  Transit-Theodolite  No.  11, 
page  212. 


Triangulation  Transit- Theodolite. 

For  use  in  Cities,  by  Colleges,  and  in  Bridge  and  Tunnel  Construction. 

No.  lid.  Plain  Transit-Theodolite  with  three  leveling  screws,  as  in 
cut  on  opposite  page,  but  without  reading  glasses  to  horizontal  circle,  also  with- 
out level,  clamp,  tangent  screw,  vertical  arc  and  striding  level  to  telescope.  Yoke 
standard  frame  is  of  aluminum  and  of  pattern  shown  in  No.  llg. 

Specifications :  — 

Horizontal  circle  6^-inch,  single  opposite  verniers  (as  in  fig.  5,  page  38)  reading 
to  2O",  glass  protected  graduation  and  verniers,  one  row  of  figures  0°  to  360°  clockwise; 
12-inch  inverting1  telescope,  aperture  1^-inch,  power  28  diameters,  achromatic  eye- 
piece ;  telescope  is  reversible  over  the  bearings  and  through  the  standards ;  long  com- 
pound centers  of  hard  bell  and  phosphor  bronze  metal;  shifting  center  (see  page  52). 
Mahogany  box  contains  reading  glass,  screwdriver,  wrench,  adjusting  pins,  etc. 

Made  to  order  only. 

Code  word,  Mobeda. 

"Weight  of  instrument  about  14  Ibs. 

"          *'  tripod  about  I3l/z  Ibs. 
Gross  weight,  securely  packed  in  two  boxes  for  shipment,  about  60  Ibs. 

Price  of  Plain  Transit-Theodolite  No.  lid,  with  three  leveling  screws, 
as  described  above $245.OO 


For  Extras  to  Plain  Transit-Theodolite  No,  lid  see  Extras  to  Plain 
TiAnsit-Theodolite  No.  11,  page  212. 


215 


No.  llf. 
Complete  Transit- Theodolite. 

For  use  in  Cities,  in  Tunnels,  ami  for  Triangulation. 
As  made  by  C.  L,.  Berger  &  Sons. 

Xo.  llf.  Size  and  particulars  are  in  all  respects  like  those  desc:  ibed  under  No. 
11,  page  212,  and  No.  lid,  page  214,  but  having  three  leveling  screws,  reading  glass- 
es to  horizontal  circle,  level,  clamp,  and  tangent  screw,  five-inch  vertical  arc,  gradien- 
ter,  fixed  stadia  wires,  and  striding  level  to  telescope  as  shown  above. 

Made  to  order  only. 

Codeword,  Mobekia 

Price,    $343.OO 

For  Extras  see  Extras  to  Plain  Transit-Theodolite,  page  212. 

(For  Code  "Words  for  Transit-Theodolite  and  P^xtras  and  changes  see  page  J, 
Complete  Code  at  back.) 


210 


No.  11  m. 
7-iiich  Complete  Transit-Theodolite, 

SPECIFICATIONS  :- 

No.  11  111  Transit-Theodolite  as  in  cut  011  opposite  page. 

Horizontal  circle  7-inch,  single  opposite  verniers  reading  to  1O",  one  row  of 
figures  0°-360°  clock-wise,  reading  glasses  to  horizontal  circle. 

Vertical  circle  5-inch,  with  one  double  vernier  at  eye  end  reading  to  single  min- 
utes, one  row  of  figures  from  0°-90°-0°. 

Level  to  vernier  frame  with  reversible  tangent  screw. 

Telescope  12-inch  inverting,  aperture  1^-inch,  achromatic  eye-piece,  power  28  dia., 
telescope  reversible  over  the  bearings  as  well  as  through  the  standard  frame  and 
provided  with  reversible  clamp  and  tangent  screw. 

Striding  level  at  points  of  contact  in  wyes. 

Stadia  wires  fixed. 

Long  compound  centers  of  hard  bell-metal. 

Shifting  center. 

Standard  frame  of  aluminum,  leather-finish. 

Split-leg  tripod. 

Instrument  packs  in  one  box  of  mahogany. 

Made  to  order  only 

Weight  of  instrument  about  14  Ibs. 

"          "  tripod  about  13^  Ibs. 
Gross  weight  packed  in  2  boxes  ready  for  shipment,  about  60  Ibs. 

Code  word,  Mobeky  Price,     $385.OO 

Extras  to  Transit- Theodolite  No.  11  in. 

Steel  centers  running  in  sockets  of  cast  iron  to  insure  freest  motion 

with  perfect  fit $20.00 

Two  double  opposite  verniers  to  vertical  circle  (as  in  cut  page  214,  in 

place  of  one  double  vernier  only  at  eye  end) 10.00 

Two  reading  glasses  to  vertical  circle      .         „        »        «        „        <>        0        »  10.00 

6-inch  spirit  level  to  telescope         „  16.00 


217 


No.  llm. 
7-inch  Complete  Transit-Theodolite. 

For  use  in  Cities,  Colleges,  State  ami   Boundary-Line  Surveys 
For  Size,  Price  and  Particulars,  see  preceding  page. 


218 


No.  llg, 
7-inch  Complete  Triangulatioii  Transit- Theodolite. 

SPECIFICATIONS  :  — 

Xo.  1  Ig  Transit-Theodolite,  as  in  cut. 

Horizontal  circle  7-inch,  one  row  of  figures  0°  to  360°  clockwise,  single  opposite 
verniers  reading  to  1C". 

Vertical  circle  5-inch,  open-form  face  graduation,  glass  protected  verniers,  one  row 
of  figures  0°  to  360°  clockwise,  single  opposite  verniers  reading  to  30". 

Level  to  vernier  arm  with  reversible  tangent  screw. 

Reading'  glasses  to  horizontal  and  vertical  circles. 

Telescope  12-inch  inverting,  aperture  1^  inch,  power  29  diameters,  telescope  re- 
versible over  the  bearings  as  well  as  through  the  standards  and  provided  with 
reversible  clamp  and  tangent  screw. 

Spirit  level  to  telescope,  6-inch. 

Striding  level  at  points  of  contact  in  wyes. 

Stadia  wires  fixed. 

Gradienter. 

Shifting  center. 

Standard  frame  of  aluminum,  leather-finish. 

Made  to  order  only. 

Codeword,  Mobello. 

Price  as  above,    $466.OO 

This  instrument  with  steel  centers  running  in  sockets  of  cast  iron  to  insure  freest 
motion  with  perfect  fit extra  2O.OO 

Weight  of  instrument  about  16  Ibs. 
"          "  tripod  about  14  Ibs. 

Gross  weight  of  instrument,  complete,  packed  securely  for  shipment  ;n  2  boxes, 
about  60  Ibs.  . 


211) 


As  made  l>y 
C.  L.  Berger  &  Sons 


7-inch  Complete  Transit- Theodolite. 

For  use  in  Cities,  Triangulation,  Tunnels,  Colleges  and  Boundary-Line  Surveys. 

For  size,  weight,  particulars  and  extras  of  this  instrument, 
see  opposite  page. 


220 

No.    12. 
8-iiich  Transit  for  Triangulation. 

As  made  by  C.  L,.  Berger  &  Sons. 

No.  1 2.  The  form  of  frame  chosen  for  mounting  the  telescope  is  similar  to  that  in  the 
cut,  which  permits  the  reversal  of  the  telescope  through  the  standards  as  well  as  over  the 
bearings.  It  is  of  improved  design  and  somewhat  resembles  that  shown  on  page  219.  It  is  very 
stiff  and  very  steady  in  strong  winds,  and  being  of  aluminum,  very  light. 

The  inverting  telescope  has  a  clear  aj)erture  of  1  \  inches,  focal  length  of  13J  inches,  power 
28  to  32  diameters,  reversible  clamp  and  tangent;  six-inch  vertical  arc  graduated  to  read  to 
30*  by  a  double  vernier  between  the  legs  of  the  standard  frame,  figures  run  from  0°  to  about 
45°  each  way.  The  horizontal  axis  of  the  telescope  is  provided  with  a  4^-inch  striding  level 
resting  at  points  of  contact  in  wyes.  The  horizontal  circle  is  8  inches  in  diameter,  single  op- 
posite glass-covered  verniers  reading  to  10",  one  row  of  figures  0°  to  360°  clockwise,  with 
reading  glasses.  The  radius  of  the  three  leveling  screw-base  is  larger  than  usual,  and  as  the 
head  of  the  tripod  is  proportionately  larger,  the  instrument  has  great  stability.  It  is  provided 
with  a  shifting  center.  The  Yoke  standard  frame  will  be  japanned  or  cloth  finished,  as  we 
deem  it  best.  In  this,  as  in  all  our  instruments,  the  fine  appearance  and  general  character 
depends  principally  on  simplicity  of  design,  coupled  with  fine  workmanship,  and  a  high  state 
of  efficiency  of  every  part.  Other  parts  that  cannot  easily  be  finished  and  lacquered  in  the 
usual  —  but  mostly  antiquated  —  manner,  are  therefore  also  treated  in  japan. 
This  is  in  line  with  good  taste  and  modern  thought  and  improvements,  to  enable  us  to  unite 
as  many  pieces  as  possible  in  one  to  secure  great  stability  and  steadiness  under  all  conditions 
in  order  to  arrive  at  quick  and  thoroughly  reliable  results.  Made  to  order  only. 

Weight  of  instrument,  18£  Ibs.;  weight  of  tripod,  19  Ibs. 

Price  .as  above,  $4O5.OO 

This  instrument  without  arc  and  clamp  to  telescope,  less  $35.OO 

No.  12a  Transit  with  a  six-inch  full  vertical  circle  (instead  of  with  arc  as  shown  in 
cut)  vernier  frame  all  open  as  in  style  No.  lib  page  214,  single  opposite  verniers 
reading  to  30",  one  row  of  figures  0°  to  360°  clockwise,  reading  glasses,  level  to  vernier 
arm $443.OO 


No.  12b  Transit  with  a  six-inch  vertical  circle  with  protected  open-form  vernier  frame, 
face-graduation,  single  opposite  verniers  glass-covered,  as  shown  in  cut  page  219,  reading 
to  20",  one  row  of  figures  0°  to  360°  clockwise,  reading  glasses,  level  to  vernier  arm, 

$473.OO 


Illumination  of  Cross  Wires  by  Mir- 
ror, Electric  Bulb  and  Dry  Battery. 

This  feature  with  the  battery  attached  to  a 
tripod  leg  is  very  convenient,  but  is  open  to  the 
objection  that  the  small  mirror*  placed  as  it  is  in 
the  center  of  the  telescope  cuts  out  the  best  rays 
of  the  object  glass  and  at  a  point  where  they  al- 
ready considerably  converge  toward  the  eye  piece. 
For  this  reason  the  simpler  form  of  attaching  a 
reflector  in  front  of  the  object  glass  is  generally 
preferred  for  the  smaller  transits. 
Price,  when  ordered  with  Transit  Theodolites 
No.  12  to  No.  15  .  .  .  $22.OO 


*  The  mirror   can   be  removed 
minating  purposes. 


ihen    not  needed   for  illu- 


221 


No.  12. 
8-inch  Transit  for  Triangulation. 


222 


No.  15. 
8"  Alt- Azimuth. 


SPECIFICATIONS  : 


No.  15  Alt- Azimuth,  as  in  cut. 

Horizontal  circle  8",  one  row  of  figures  0  to  360 
clockwise,  single  opposite  verniers  reading  to  5". 

Vertical  circle  7",  open-form  face  graduation, 
glass-protected  verniers,  one  row  of  figures  0  to  90 
to  0,  double  opposite  verniers  reading  to  10",  red  and 
black  figures. 

Level  to  vernier  arm  with  reversible  tangent 
screw. 

Reading  glasses  to  horizontal  and  vertical  circles. 

Telescope  12"  inverting,  aperture  H",  power  30 
diameters;  telescope  reversible  over  the  bearings,  as 
well  as  through  the  standards,  and  provided  with  re- 
versible clamp  and  tangent  screw. 

Striding  level  at  points  of  contact  in  wyes,  5*.long, 
2  seconds  of  arc  for  1  division  of  2  millimeters. 


Electric  axial  illumination,  with  reflector  in 
telescope. 

Trunnions,  Invar  steel. 

Diagonal  eye-piece,  power  39  diameters. 

Centers  of  steel  or  bell  metal. 

"Wires,  5  vertical  time  wires,  with  interval  of   10 
equatorial  seconds ;  2  horizontal  wires  closely  spaced. 

Ring  on  leveling  piece,  to  lift  instrument. 

Tripod,   full   length,   split-leg,   "without   shifting 
center. 

Standard  frame  of  brass  or  aluminum,  leather 
finish.  Made  to  order  only. 

Code  word 

Price  upon  application. 

Weight  of  instrument  about  27  Ibs. 
of  tripod  about  17j  Ibs. 

Gross    weight    of    instrument  complete,  packed 
securely  for  shipment  in  2  boxes,  about  100  Ibs. 


223 


No.  15  a. 
Alt  .-Azimuth . 

Alt.- Azimuth,  as  in  cut.  Graduations  of  51A  inch  circles  on  solid  silver,  two 
opposite  micrometer-microscopes  for  each  circle  reading  to  10",  and  by  estimation 
to  2".  Botn  circles  can  be  shifted,  so  as  to  bring  different  parts  of  the  graduation 
under  the  micrometer-microscopes.  The  telescope  islO  inches  long,  has  an  aperture 
of  1%  inch  and  a  power  of  24  diameters.  Telescope  is  provided  with  a  level  on  top 
and  with  3  horizontal  wires  for  leveling  and  for  stadia  measurements,  and  if  desired 
with  5  vertical  wires  for  star  observation.  The  telescope  must  be  reversed  in  its 
bearings  by  hand.  Telescope  axis  is  of  hardened  steel.  The  striding  and  microscope 
levels  read  to  5"  of  arc.  Two  ordinary  small  levels  attached  to  the  instrument 
serve  to  place  it  in  an  approximate  horizontal  position.  Complete  in  box. 

Price,  as  above,  $58O.OO 


224 


No.  15  b. 
Alt  .-Azimuth. 


Alt. -Azimuth,  as  in  cut.  Circles  8£  inches  diameter,  micrometer-microscopes 
reading  to  5  seconds  direct,  and  by  estimation  to  single  seconds.  Telescope,  1.6  in. 
aperture;  focal  length,  16  J  inches;  power,  32  and  48.  Telescope  axis  is  of  hardened 
steel  and  balanced  by  friction  rollers.  Reversing  apparatus.  Complete  in  one  box. 

Price,  as  above,  $92O.OO 
This  instrument  without  reversing  apparatus,          ....         less,    $100.00 


15  C,  Alt.-Azimuth,  as  in  cut  above.  Circles  10£  inches  diameter,  mic- 
rometer-microscopes reading  to  single  seconds  direct.  Every  single  degree  figured. 
Telescope,  If-inch  aperture ;  focal  length,  20|  inches ;  power,  40  and  60.  Telescope 
axis  is  of  hardened  steel  and  balanced  by  friction  rollers.  Complete  in  two  boxes. 

Price,  as  above,  $13OO.OO 


225 


Portable  2"  Time   Transit   Instrument. 


As  made  by  C.  L.. 

Transit  Instrument,  as  shown,  has  2^"  clear 
aperture,  by  24.45"  focal  length,  with  one  Kellner 
eye-piece  power  of  33  diameters  and  one  large  elbow 
eye-piece  of  30  diameters;  there  are  5  time  wires, 
spaced  20  seconds  of  time  apart,  and  2  closely 
spaced  horizontal  wires;  a  reflector  in  the  center  of 
telescope  for  illuminating  the  cross  wires,  and  lard-oil 
lamp  is  attachable  to  either  side  of  standard  frame. 

The  6"  aluminum  vertical  circle  is  graduated 
on  Sterling  silver,  has  double  opposite  verniers  read- 
ing to  minutes,  with  one  row  of  figures  from  0  to 
180  to  0  for  zenith  distances;  circle  reading  0  when 
telescope  points  to  the  zenith;  reading  glasses  are 
attached,  and  a  control  level;  it  has  a  reversible 
clamp  and  tangent. 

The  stride  level  has  a  value  of  6  seconds  of  arc 
for  TY'  run,  provided  with  an  adjustable  mirror  for 
reading  the  bubble. 

The  standard  frame  is  provided  with  two  level- 
ing screws  and  one  fixed  point,  with  base  plates.  In- 


Berger  &  Sons. 

strument  adjustable  in  azimuth  by  opposing  capstan 
screws  on  one  base  plate;  finished  in  our  handsome 
leather  finish. 

The  instrument  is  packed  securely  in  two  stout 
wooden  boxes,  to  withstand  long  transportation. 

Weight  of  instrument  complete,  130  pounds. 

Gross  weight  packed  for  shipment,  260  pounds. 

If  instrument  is  to  be  used  at  several  stations,  and 
it  is  desired  to  pack  same  to  permit  of  ready  trans- 
portation from  place  to  place,  an  extra  charge  for 
this  special  packing  will  be  made. 

With  rack  motion  for  observing  transit  or  stars, 

Extra 

For  striding  level  reading  to  single  seconds  of 
arc  Extra 

Filar  micrometer,  reading  to  single  second  of 
arc  Extra 

Impersonal  micrometer Extra 

Prices  upon  application. 


Portable  Transit  Instrument  for  Latitude  Observations. 

As  made  by  C.  L.  Berber  &  Sons. 

No.  16.  Aperture  of  object-glass  3  in.;  focus  28  in.;  spider-line  or  glass 
micrometer ;  micrometer  screw  reads  to  seconds  of  arc ;  spirit-levels  read  to  seconds 
of  arc ;  diagonal  eye-piece  80  dia. ;  Ramsden  eye-piece  40  dia. ;  vertical  circle  8  in. 
India.;  bell-metal  pivots,  two  lamps  and  arms,  adjustable  reflector;  reversing 
apparatus ;  two  cases,  enc. 

Price  $980. 


227 


Portable  Astronomical  Transit  Instrument. 

As  made  for  U.  S.  Lake  Survey. 

No.  17.  Aperture  of  object-glass  3  in.;  focus  39  in.;  spider-line  or  glass  micrometer;  diagonal  eye- 
piece magnifies  from  90  to  120  dia. ;  Ramsden  eye-piece  magnifies  75  dia.;  striding  level  reads  to 
seconds  of  arc;  adjustable  mirror  to  read  the  level  from  below;  reserve  level;  pivots  of  hardened  steel; 
small  adjustable  plane  reflector;  two  lamps  and  arms;  reversing  apparatus;  two  finding  circles  each 
provided  with  double  verniers;  cast-iron  frame  rests  on  three  leveling  screws  of  steel,  which  are  pro- 
vided with  foot-plates  —  one  of  them  is  adjustable  to  set  instrument- in  the  meridian;  two  cases,  etc. 

Price $13OO.OO 

(Notice  of  this  Instrument,  with  full  description,  in  Johnson's  New  Universal  Cyclopaedia,  under 

article  "Transit.") 

The  above  instrument  provided  with  an  Impersonal  Micrometer,  U.  S.  C.  &  G.  S.  Pattern. 

Price  on  application. 


228 


Reflecting  Circle. 


Artificial  Horizon. 

Mercury  Horizon  of  boxwood,  with  silver-plated  copper  bowl;  bottle  of  bo*' 
od  for  mercury ;  brass  rectangular  roof  with  glass  coyers  made  of  parallel  glass. 
All  complete,  packed  In  a  box.    Best  quality,  imported.     .       .    Price,  $5O.OO 


229 


Sextant. 

Sextant.  Radius,  7  inches,  145° ;  four  sun-glasses  between  fche  large  and  the 
email  reflecting  mirror,  and  three  sun-glasses  behind  the  small  reflecting  mirror,  all 
of  which  can  be  turned  on  their  axis  180°;  graduation  on  solid  silver,  reading  to  10". 
telescope  f  inch  aperture ;  two  astronomical  eye-pieces  with  powers  of  6  and  10  dia. 
One  Galilean  telescope  with  extra  large  objective*  power  3  dia. ;  one  fixed  raading 
glass ;  two  sights  for  examination  and  correction  of  the  large  reflecting  mirror.  All 
complete  in  box.  Best  quality,  imported.  .  .  Price,  as  above,  $13O.OO 
Sextant,  as  above.  Radius  10  inches,  all  complete  in  box.  .  Price,  15O.OO 
Pocket  Sextant,  best  quality «s  43.OO 


Magnetometer,  according  to  design  Carnegie  Institute,  Dept.  Terrestrial  Mag- 
netism.  Price  on  application. 


Pendulum  Apparatus  for  determining  gravity.  U.  S.  C.  &  G.  S.  Pattern. 

Price  on  application. 


230 

Current  Meters, 

The  types  of  current  meters,  as  shown  in  Figs.  I,  II,  and  III,  in  our  former  Catalogues,  have  been 
omitted,  owing  to  the  many  improvements  made  and  embodied  in  the  Meter,  as  shown  in  Figs.  IV,  V,  and 
VI,  this  Catalogue.  We  are,  however,  prepared  to  make  to  order  Current  Meter  No.  Ill,  as  designed  by 
Mr.  Clemens  Herschel,  if  so  desired. 

Current  Meter  No.  IV. 

The  electric  form  of  meter  shown  in  Fig  IV  is  especially  adapted  for  observations 
upon  large  rivers,  arms  of  the  sea,  etc.  It  has  its  registering  apparatus  above  the  sur- 
face of  the  water,  or  on  the  bank  of  a  river,  and  current  measurements  may  be  made 
with  it  at  any  depth,  and  may  be  continued  for  a  week,  or  longer,  without  stopping,  if 
desired.  Half  a  dozen  or  more  of  these  meters  may  be  strung  on  one  and  the  same  ver- 
tical rod  or  wire,  and  simultaneous  observations  then  taken  of  the  velocities  at  different 
depths  below  the  surface. 

This  form  was  used  upon  the  gauging  of  the  Connecticut  River*  by  General  Ellis, 
and  was  designed  particularly  to  avoid  the  catching  of  floating  substances,  such  as 
leaves  and  grass,  upon  either  the  vanes  or  the  axis,  and  to  render  the  record  of  the 
instrument  independent  of  the  position  of  its  axis  with  respect  to  the  line  of  the  current, 
also,  to  get  less  friction  upon  the  axis  so  as  to  measure  low  velocities  accurately. 

This  current  meter  is  constructed  upon  the  principle  of  Robinson's  Anemometer,  turning  by  the  difference 
of  pressure  upon  opposite  vanes  of  the  wheel.  The  vanes  of  this  meter,  however,  instead  of  being  hemispher- 
ical cups  with  a  straight  stem,  are  made  conical  at  the  ends,  and  are  hollow  and  taper  to  the  central  hub,  so  as 
to  offer  no  obstruction  to  the  slipping  off  of  straws,  leaves,  or  grass,  as  the  wheel  revolves.  The  central  hub 
is  made  tapering,  so  that  any  object  can  slide  off  easily,  and  it  extends  over  the  joints  at  the  ends  of  the  axis, 
so  as  to  enclose  and  protect  them  from  floating  substances.  The  axis  runs  in  iridium  bearings.  The  forward 
end  of  the  frame  which  carries  the  wheel  can  be  turned  and  secured  in  any  position,  so  that  the  wheel  can  be 
horizon  tal/vertical,  or  at  any  desired  angle. 

The  electrical  connection  is  made  by  carrying  an  insulated  wire  from  near  the  center  of  the  instniment, 
where  the  insulated  wire  from  the  battery  is  attached  to  it  by  a  binding  screw  when  in  use,  out  to  the  end  of 
one  arm  of  the  wheel  frame,  where  it  ends  in  a  fine  platinum  wire  resting  upon  a  ring  in  the  hub  of  the  whee^. 
This  ring  is  made  of  alternate  interchangeable  sections  of  silver  and  hard  rubber,  secured  in  place  by  screws, 
so  that  their  position  can  be  changed  to  register  whole  or  part  revolutions  as  desired.  There  is  also  a  socket 
and  set-screw  in  the  body  of  the  frame  near  the  center,  for  the  return  current,  which  can  be  carried  through  a 
plain  wire  slightly  twisted  around  the  insulated  wire  so  as  to  form  one  cord.  If  the  instrument  is  run  upon  a 
wire,  or  has  a  metallic  connection  with  the  surface,  the  return  current  can  be  made  through  that.  A  better 
method  now  in  vogue  is  to  use  a  "  twin  "  insulated  wire. 

The  universal  motion  at  the  center  of  the  frame  and  the  tail  are  of  the  usual  construction.  This  meter 
can  be  used  in  connection  with  any  apparatus  for  registering  the  revolutions  of  the  wheel  by  the  breaks  in  the 
electric  circuit. 

Price  complete,  as  in  Fig  IV,  with  electric  register  and  one  battery 

etc.,  packed  in  three  cases,      ........         .     $195.OO 

Price  of  this  instrument  without  electric  register  and  battery  .        .        .       135.OO 

*  For  further  information  on  this  point,  see  Gen'l  G.  K.  Warren's  Report  of  Surveys  and  Examinations 
of  Connecticut  River. 

We  can  have  this  meter,  as  well  as  Nos,  V  and  VI,  carefully  rated  at  an  additional  expense  of  from 
$15.00  to  $25.00.  Unless  ordered  otherwise,  the  instruments  will  be  sent  unrated. 

Current  Meters  No.  V  and  No.  VI. 

This  form  of  Current  Meter,  invented  by  Fteley  &  Stearns,!  and  illustrated  on  page 
198,  is  specially  adapted  for  observations  upon  smaller  rivers,  streams,  conduits,  flumes, 

etc.  The  3%  inch  wheel  has  vanes  of  true  standard  screw  pitch  welded  to  the  rim  and 
axle  and  is  perfectly  balanced.  All  edges  are  sharp  to  cut  the  water  to  avoid  eddies. 
Its  axle  is  provided  with  points  of  iridium,  so  as  not  to  be  affected  by  grit  in  the  water 
and  to  run  in  the  bearings  with  minimum  friction.  These  points,  combined  with  ac- 
curate workmanship  and  good  design,  insure  a  permanent  and  unvarying  rating  curve. 

The  instrument  is  provided  with  a  registering  apparatus,  the  dial  wheels  of  which 
are  completely  protected  by  a  glass  cover  readily  removable  at  will.  This  counting 
mechanism  is  operated  by  a  string,  by  means  of  which  the  dial  wheels  are  thrown  in 
and  out  of  gear.  One  short  pull  throws  them  in  and  the  next  pull  throws  them  out  ; 
next  in,  and  so  on. 

Guards  placed  over  this  mechanism  and  the  wheel  protect  them  from  injury  and 
floating  substances.  Those  of  the  wheel  are  far  removed  from  it  to  avoid  checking  the 
flow  of  water. 

For  more  extended  observations  upon  rivers,  etc.,  a  separate  electric  register  and 
battery,  shown  on  page  232,  can  be  supplied  with  this  instrument. 

Price  of  Current  Meter  No.  V,  supplied  only  with  the  ordinary 
registering  apparatus,  as  shown  in  the  main  cut  on  page  232,  and  with 
12  feet  of  brass  tubing,  made  in  sections  of  four  feet,  and  graduated  in 
feet  and  tenths.  Complete  in  two  cases,  ......  $135.OO 

Price  of  Current  Meter  No.  VI,  in  all  respects  similar  to  that  above, 
but  in  addition  to  the  ordinary  registering  apparatus  this  instrument  is 
provided  with  an  electric  register,  one  battery  and  copper  wire,  as 
shown  in  the  smaller  cuts  on  page  232.  Complete  in  four  cases,  .  .  $195.OO 

•j-  For  further  information  on  this  Current  Meter,  read  "  Description  of  some  experiments  on  the  Flow 


of  Water,  made  during  the  Construction  of  Works  for  Conveying  the  Water  of  Sudbury  River  to  Boston,"  by 
.  Stearns  (Transactions  of  the  Society  of  Civil  Engineers,  Jan.-March,  1883).  Also,  "  On 
,  together  with  a  Reason  why  the  Maximum  Velocity  of  Water  Flowing  in  Open  Channels 

is  Below  the  Surface,"  by  F.  P.  Stearns;  a  paper  read  at  the  Annual  Convention  of  the  American  Society  or 


231 


This  meter  can  be  arranged  to  reg- 
ister  single   revolutions   and    every    5 
revolutions. 
Price,  extra      ....    $15.OO 


Current  Meter  No.  IV. 

As  made  by  C.  L.  Berger  &  Sons. 


232 


Current  Meters  No.  V  and  VI, 

As  made  by  C.  L..  Berger  &  Sons. 

For  price,  etc.,  seepage  230. 

This  No.  VI.  meter  can  be  arranged  to  register  single  revolutions  and  every  5 
revolutions.    Price,  extra     . $15.OO 


For  the  convenience  of  our  customers  we  append  a  list  of  miscellaneous  articles  kept  in 
stock,  but  most  of  them  are  not  of  our  manufacture.  Those  not  made  by  us  are  of  the  best 
quality  obtainable,  and  the  prices  quoted  are  identical  with  those  in  the  market. 

Precision  Pantographs. 


The  arms  of  these  Panto-  /"••s^^mp^^Sf'lo  graphs,  to  avoid  friction  on  the  paper,  are  suspended 
from  a  solid  iron  support  (as  will  ^HrlSw  jl£f!)  be  seen  in  cut),  the  latter  being  supplied  with  levels 
and  leveling  screws.  The  instru-  /  I  I  ment  is  capable  of  enlarging  or  reducing  in  all  ratios, 

and  is  very  useful  for  copying.  The    brass    arms   are    hollow   and   square    in    cross- 

section,  and  are  divided  to  millimeters  with  verniers  reading  to  -J^  mm.  For  the  accurate  setting  of  the 
verniers  slow  motion  screws  are  provided.  All  swivel  pints  turn  upon  center  points.  The  disengaging  mech* 
anism  is  a  special  convenience.  The  ratios  from  |  to  ^7f  are  set  with  pole  at  end,  those  from  3  to  T  to  jf 
are  set  in  the  middle.  The  pole  and  pencil-holder  are  therefore  interchangeable. 

No.  99.   Suspended  Pantograph,  arms  about  24  inches  long,  in  wooden  case. 

Price,  as  above,  $15O.OO. 
No.  100.   Suspended  Pantograph,  arms  about  38  inches  long,  in  wooden  case. 

Price,  as  above  $18O.OO. 

NOTE. — The  Pantograph  with  24-inch  arms  when  set  at  5  can  circumscribe  a  ig-inch  square,  or  an 
oblong  155  x  24  inches,  approximately. 

The  Pantograph  with  38-inch  arms  can  circumscribe  a  3i-inch  square,  or  an  oblong  275  x  39  inches, 
approximately. 

Compensation  Planimeter. 


The  compensation  Planimeter  illustrated  above  consists  of  two  parts,  which  pack  separately  in  the  case, 
the  tracing  frame  and  the  pole  arm.  The  tracing  frame  rests  on  3  points,  the  measuring  wheel,  the  tracer 
point  and  the  roller.  A  finely  polished  steel  ball,  fixed  at  one  end  of  the  pole  arm,  rests  in  an  opening  of  the 
tracer  arm,  forming  a  ball  and  socket  joint.  This  joint  forms  the  axis  of  rotation  of  the  tracer  arm.  which  by 
means  of  the  pole  arm  moves  on  a  circle  as  guide  line  ;  at  the  same  time  it  enables  the  tracing  frame  always  to 
rest  with  its  three  points  on  the  plan.  The  length  of  tracer  arm  is  about  9  1-2  inches  and  pole  arm  7  1-2  inches. 

The  pole  consists  of  a  brass  cylinder  attached  at  one  end  of  the  pole  arm.  Its  lower  surface  forms  an 
edge  at  right  angles  to  the  pole  arm,  which  by  the  rocking  motion  provided  by  this  edge  can  be  lowered  until 
its  other  end,  which  carries  the  ball,  is  firmly  secured  in  the  socket.  In  the  center  of  this  brass  cylinder  a 
simll  steel  pin  is  inserted  and  kept"  in  place  by  a  set  screw.  This  pin  terminates,  at  both  ends  in  a  finely 
hardened  point,  one  of  which  projects  slightly  under  the  lower  edge  of  the  cylinder.  The  tracer  arm  is  pro- 
vided with  a  vernier  and  micrometer  screw  by  which  it  can  be  placed  at  any  division  mark  on  the  tracer  arm, 
which  is  graduated  throughout  in  1-2  mm.  The  axle  of  the  measuring  wheel,  ending  in  finely  made  pivots,  is 
of  the  be-*,  hardened  steel  working  in  cylindrical  steel  point  bearings.  With  tl  e  Planimeter  is  supplied  a 
proving  bar,  which  enables  by  its  graduations  to  describe  several  circles  of  known  radii. 

In  using,  place  the  Planimeter  approximately  in  the  center  of  the  area  to  be  measured,  so  that  the  plane  of 
the  measuring  wheel,  if  extended,  passes  through  the  pole.  After  obtaining  the  measurement  by  using  the 
Planimeter  with  the  pole  arm  on  one  side  of  the  tracer  arm,  the  pole  arm  may  be  placed  on  the  other  side  and 
another  measurement  made.  The  mean  of  these  two  readings  will  eliminate  any  error  ol  the  measuring  wheel, 
thus  this  form  of  instrument  is  a  compensation  Planimeter. 

If  the  area  to  be  measured  is  too  large  for  the  scope  of  the  instrument  it  should  be  subdivided  into  smaller 
areas.  According  to  the  importance  of  results  to  be  obtained,  one  measurement  may  be  sufficient  around  the 
plan,  but  when  very  accurate  results  are  desired  it  will  be  good  practice  to  make  2  or  3  consecutive  measure- 
ments with  the  pole  arm  on  one  side  of  the  tracer  arm  and  afterward  the  same  number  of  consecutive  read- 
ings with  the  pole  arm  on  the  other  side  of  tracer  arm,  and  by  taking  the  mean  of  the  averages  of  readings 
obtained,  very  close  results  will  be  obtained. 

The  Compensation  Planimeter  is  made  of  German  silver  and  bronzed  brass. 
The  tracer  arm  is  adjustable  and  graduated  to  the  end,  pole  weight  of  improved  pat- 
tern. Instrument  complete  in  velvet-lined  case,  with  table  of  constants  for  U.  S. 
standard  measure,  adapting  it  to  any  scale. 

Xo.  107.    Price  complete  as  above          . 3O.OO 

"No.  108.        "  "        "       "     when  specially  rated          .        .        .        34.OO 


234 


Plain  Polar  Plaiiimeter. 


This  Planimeter  is  of  German  silver,  with  adjustable  tracer  arm  fully  gradu- 
ated, about  9  inches  long,  in  polished  mahogany  box  with  proving  bar. 

Price  of  instrument  when  rated       ...          .         .  .  $31.00 

not  rated  but  with  all  the  improvements  27.00 

Precision  Plaiiimeters. 

These  Planimeters  are  very  much  more  accurate  than  the  ordinary  Polar  Plani- 
meters.  The  graduated  rollers  do  not  touch  the  paper  at  all,  but  roll,  instead,  on  a 
hard,  highly  polished  surface  of  steel,  thus  eliminating  all  errors  due  to  the  irregu- 
larities of  the  paper  surface. 

No.  1O9.    Large  Suspended  Ball  Plaiiimeter. 


Not  kept  in  stock. 


This  instrument  is  capable  of  doing  very  accurate  work.  The  tracer  arm  is  11| 
Inches  long,  the  pole  arm  is  6£  inches  long,  and  the  diameter  of  the  toothed  circle  on 
the  pole  is  6£  inches.  The  angular  motion  of  the  tracer  arm  is  about  90°. 

Surfaces  from  2£  x  4  inches  to  7  x  10  inches  can  be  measured  without  moving  the 
pole. 

Price  of  instrument  complete  packed  in  morocco  box         .        .        .        $75.00 

No.  11O.     Large  Rolling  Ball  Planimeter. 


The  Planimeter  illustrated  above  is  made  of  German  silver  and 
bronzed  brass,  and  enables  to  obtain  results  of  greater  accuracy  than 
any  other  Planimeter  yet  made,  both  on  large  and  small  surfaces     The 
tracer  arm  is  graduated  throughout  and  has  a  length  of  12  inches  which  can 
be  increased  by  a  lengthener  to  22  inches.     Its  angular  motion  is  about  00° 
Ihe  two  rollers  are  made  of  exactly  equal   diameters,  ensuring  a  motion  of  the 
instrument,  as  a  whole,  in  a  straight  line.     A  surface  of  any  length  and  a  width  of 
20  inches  can  be  measured  with  the  22  inch  tracer  arm. 

Price  of  instrument,  with  testing  bar  enabling  to  check  areas 
of  known  radii,  and  table  of  settings,  in  velvet-lined  morocco  box 
with  lock 


$9O.OO 


Surveyors'  Pocket  and  Marine  Compasses. 


No.  115. 


No.  112. 

"  113. 

"  114. 

"  115. 

"  116. 

"  117. 

"  117a. 

"  118. 

"  119. 

"  120. 


No.  117. 


Pocket  Compass,  with  folding  sights,  2}4  inch  needle,      . 
"         2)4  inch  needle,  Jacob  Staff  mountings, 


$  8.00 
.      10.00 
12.00 
"  with  level,  folding  sights,  4-inch  needle,  with  ball  and 

socket  joint, 13.50 

Vernier  Pocket  Compass,  4^  inch  needle,  "  Tripod  "  and  2  levels     .          23.00 
Prismatic  Compass,  complete,  with  azimuth  glasses,  and  divided  alumi- 
num ring,  3  inch  Leather  Sling  Case.    Best  kind,      ....      30.00 

Hutchinsbn's  Prismatic  Compass  bronzed,  of  improved  pattern  nearly 

enclosed  top,  floating  card  dial,  2  inch,  in  morocco  case 
Pocket  Compass,  watch  pattern,  brass,  1>£  inches  in  diameter  with 
hinged  cover  and  stop  to  needle,         ...  ... 

Pocket  Compass,  gilt,  watch   pattern,  with  stop,  enamelled  dial  and 

agate  centre ;  1  or  2  inches  in  diameter 

Ritchie's  Patent  Liquid  Compasses,  of  all  sizes,  from  $33.00  to  $35.00, 
$45.00  and  $55.00.  

Miners'  Compasses. 


11.00 

1.75 
5.00 


No.125. 

No.  125.  Miners'  Compass,  provided  with  stop  and  glass  covers,  for  tracing 

iron  ore,  3  inch  Norwegian  needle, $16.00 

**   126.  Miners'  Compass,  provided  with   stop  and  glass  covers,  4  in.  Nor- 
wegian needle,    .  20.00 


236 


Leveling  Rods 


No.  145 


No.  147 


No.  150 


237 

Leveling-  Rods 

The    leveling'    rods   illustrated 

are  of  best  make  and  are 

always  carried  in  stock. 

No.  145.  New  York  Rod.  6T"ff 
ft.  extending  to  12  ft.,  reading  by  vernier 
to  lOOOths  of  a  foot,  with  improved 
mountings  .  .  .  $14.OO 

No.  145  a.    Extra  Target  for 

N.  Y.  Rod  for  use  with  gradienter  or 
stadia  measurements        .         .      5.OO 

No.  146.    Philadelphia  Rod, 

self  reading,  7^  ft.  extending  to  13  ft., 
reading  by  vernier  to  lOOOths  of  a  foot. 

14.OO 

No.  146 a.  Extra  Target  for 
Philadelphia  Rod  .  .  5.OO 

No.  147.    Boston  Rod.    6   ft. 

extending  to  11  ft.,  reading  by  vernier 
to  lOOOths  of  a  foot        .        .      14.OO 

No.  148.    Mining   Rod.     Philadelphia  pattern 
like  No.  146,  6  ft 12.OO 


Ranging  Poles 


No.  149 


No.  148  a.    Mining  Rod.     Philadelphia  pattern 
like  No.  146,  3£  ft.     .        .                 .         .            12.OO 

No.  148  b.     Mining  Rod.     N.  Y.  pattern  like 
No.  145,  5  ft  1  2.OO 

1 

No.  148  c.     Mining  Rod.      X.  Y.  Pattern  like 

No.  146,  31,  ft.             12.OO 

No.  149.  Flexible  Self-reading  Level  Rod. 

10   ft.  long,  3  inches  wide.     This  rod  is  graduated  on 
canvas  and  can  be  rolled  up.     When  used  it  is  fastened 
upon  a  board  with  thumb-tacks        .         .         .       3.25 

No.  15O.     Metric  Level  Rod.     Philadelphia 
pattern,  2  meters  to  3.7  meters           .         .             14.OO 

No.  151.    Metric  Level  Rod.     N.  Y.  pattern, 
2  meters  to  3.  7  meters         ....            14.OO 

No.  151  a.    Rod  Level  for  plumbing  rod      3.OO 

Ranging  Poles 
Painted  red  and  white  alternately 
each  foot. 

No.  152.    Range  Pole.    Solid  steel  octagon, 

6  ft.,  *  inch  dia  3.OO 

No.  153.    Range  Pole,  iron  tube  round, 

6  ft.,  1  inch  dia          2.75 

No.  154.     Range   Pole   of  wood,  8  ft.,  steel 
shoe           2.25 

No.  155.     Range  Pole,  like  No.  1.54  but  1  O  ft. 
2.50 

:, 
i 

fc..-;fe 


Nos.  152      153 


154 


Paine's  Steel  Tape  Measures. 

&  inch  wide.    In  Leather  Cases,  with  flush  handles. 


So.  160.  100  feet  Paine's  Steel  Tape,  divided  in  lOths,  ....     $11.00 

u    161.    50    "        u  "  "  600 

"   162.  100    "        "  "  l>  on  one  side,  on  the  other 

in  centimeters,          ...        c        ......        15.00 


Chesterman's  Steel  Tape  Measures. 

%  inch  wide.    In  Leather  Boxes. 


No.  163.  100  feet  Chesterman's  Steel  Tape,  divided  in  lOths,     . 
tk    164.     66     u  tk  "  "  u 

u    165.     50    u  u  u  u  u 

*«   166.    33    "  "  ';  u  "     . 


$11.00 

8.00 

.     6.00 

5.00 


Pocket  Steel  Tape  Measures. 

In  German  Silver  Cases,  with  spring  and  stop. 

No.  167.  3  feet  long,  divided  in  lOths 80 

"    168.  5     kk       "  "  *'  . 1.10 

**    169   5    ""      4k            u               u      on  one  side,  and  in  centimeters  and  mil- 
limeters on  the  other  side,      1-25 


239 


Steel  Tape  Measures. 

i/2  inch  wide.    Patent  Brass  Frame  with  Handle. 


No.  170.   100  feet  Steel  Tape,  divided  in  lOths,     . 
«    171.     50    " 


Steel  Tape  Measures. 

inch  wide.    In  Leather  Boxes. 


No.  172.   100  feet  Steel  Tape,  divided  in  lOths, 
"    173.     66    "        "         "  " 

"    174.     50    " 


liufkin  Steel  Tape  Measures, 

%  inch  wide.    In  leather  case. 


$11.50 
6.60 


$11.50 
8.00 
6.50 


206.  D. 

203.  D.         ^^^^^  103.  D. 

No.  206.  D.  100  feet  Lufkin  Steel  Tape,  divided  in  lOths,         . 
No.  203.  D.     50    "  "  "  " 

No.  103.  D.    50   "          "          "        "  "  "  |    inch 

inchdia.;  5  oz.  in  weight;  can  be  carried  in  vest  pocket  . 


wide; 


$11.00 
6.00 

4.00 


240 


Surveyors'  Chain  Tapes. 

Heavy  J^-inch  Steel  Tapes. 

Graduations  etched  on  bright  raised  surfaces. 
Graduated  to  single  feet,  end  feet  to  tenths  (one  side  only). 


No.  175. 


No.  17oa.     100  feet,  complete  with  reel 
"     175b.    200    "  "  "      « 

"     175c.    500    "  "  "      " 


$7.50 
10.50 
21.50 


No.  176. 


No.  176a.     100  feet,  complete  with  reel 
"     176b.    200    "  "      " 

'4     176c.     6QP     •  "  *«      "    . 


$7.50 
10.60 
21.50 


241 


Lucas's  Improved  Steel  Tapes. 

%  incli  wide. 

All  tapes  of  this  manufacture  are  made  from  the  best  quality  of  clock-spring  steel, 
one-fourth  of  an  inch  wide,  and  of  thickness  best  adapted  to  strength  and  flexibility, 
tempered  straight,  and  graduated  under  tension,  being  drawn  on  steel  bars  made  to 
correspond  with  U.S.  standard,  and  are  guaranteed  to  be  as  accurate  as  any  tapes  made 

in  this  country.  The  graduations  are  made  each 
five  feet  or  links,  according  to  the  style  of  tape, 
by  brass  or  german  silver  bands  firmly  soldered 
to  the  tape,  and  marked  each  side  with  plain 
figures  in  such  a  manner  as  to  be  conveniently 
read  from  either  end  without  liability  of  error 
in  count.  The  intermediate  points  of  feet  or 
links  are  marked  by  a  small  brass  rivet  through 
the  tape,  with  raised  head  on  each  side  so  as  to 
be  easily  seen.  Each  end  foot  on  Engineers' 
tapes  is  graduated  to  tenths  of  a  foot.  The  ad- 
justments for  taking  measure  are  so  arranged 
that  no  difference  is  made  by  the  use  of  large 
or  small  marking  pins,  the  measurement  being  made  and  taken  from  the  same  side  of 
the  pin.  Soldering  of  the  number  bands  secures  them  from  peeling  up  or  rusting 
underneath.  The  method  of  numbering  avoids  the  necessity  of  changing  ends  of 
tape,  it  works  same  with  either  end  forward. 

No.  178  D.     100  feet,  Engineer's,  graduated  to  feet,  each  five  feet  by  soldered 

bands  marked  with  figures,  end  leet  to  tenths  of  a  foot $4  00 

No.  178  K.    66  feet,  Surveyor's,  graduated  to  links,  with  figured  bands  every  five 

links 3.50 

Metal  Reel,  $2. 00  extra.     Ring  handles  included  in  price  of  tape. 
Tension  and  Temperature  sent  with  each  tape  when  sold 

Roe's  Steel  Tapes   on  Brass  Reel. 

\i  inch  wide. 

These  tapes  are  made  of  superior  steel, 
%  inch  wide,  graduated  every  foot  by  a 
brass  rivet,  end  feet  in  tenths.  Every  five 
feet  has  a  brass  plate  with  the  numbers, 
and  every  ten  feet  has  a  copper  plate 
with  numbers. 

They  are  graduated  from  a  standard 
tape  certified  to  by  an  official  of  the 
U.  S.  Coast  Survey  Department  as  cor- 
rect at  a  temperature  of  62°  F. 

No.  179  1  A.     100  feet  long,  graduated  every  foot,  end  feet  in  tenths,        .        $5.00 
7A.      50    "      "  "  "         "      "        "    "       "  .          4.00 

Prices  above  include  a  Patent  Brass  Reel  and  pair  of  Patent  Brass  Detachable 
Handles. 

Brass  Reel,  without  Tape, SI. 50 

Detachable  Handles,  per  pair, 0.30 

Tape  Repairer 


No.  179  P. 


Tape  Repairer 
1000  Eyelets 
Complete  Outfi; 


$2.75 

1.25 
(postage  17  cents  extra)        4.00 


NOTE. — This  repairer  cuts  a  clean  hole  one-sixteenth  of  an  inch  in  diameter  through  two  thicknesses 
of  the  ordinary  engineer's  tapes,  such  as  Lufkin's,  Chesterman's,  etc.  No  filing  is  required  except  to  round 
the  rough  corners  of  the  break.  Place  the  tape  on  the  rubber  pad  and  punch  the  hole  in  the  required  place. 
Next  place  an  eyelet  on  the  pivot  provided  for  it,  insert  it  in  the  hole  and  rivet  it.  The  first  rivet  holds  the 
tape  in  position  for  cutting  and  riveting  the  rest.  Repairs  ran.  be  made  quickly,  without  any  danger  of  split- 
ting the  tape,  thus  avoiding  any  chance  of  dirt  collecting  under  the  splices,  of  cutting  the  fingers  when  draw- 
ing the  tape  through  the  hands,  or  catching  in  rags,  etc.,  when  cleaning. 


2-12 


Standard  Steel  Tape  Measures. 

For  city  and  bridge  engineering,  in  lengthg  from  100  to  1000  feet. 


No.  180. 


These  tapes  are  of  exact  United  States  Standard  and  have  no  joints.  They  are 
*$enerally  made  in  lengths  of  300  feet  with  graduations  at  every  10  feet,  the  last  1C 
feet  graduated  in  single  feet,  and  the  last  foot  into  lOths.  For  railroad  and  under- 
ground work  we  frequently  furnish  them  in  lengths  of  400  and  500  feet.  A  clamping 
handle  can  be  furnished  to  attach  to  the  tape  at  any  desired  length,  if  shorter 
measures  than  the  whole  length  are  intended  to  be  made.  We  also  can  furnish  a 
small  brass  clamp  to  fasten  on  the  tape  in  order  to  mark  lengths  that  are  used  re- 
peatedly. 
Price  of  tape  100  feet,  graduated  at  every  10  feet,  the  last  10  feet  graduated 

in  single  feet,  the  last  foot  in  lOths, 

Price  of  tape  200  feet,  graduated  as  above, 

"      "       "     300     "  "  "       " 

"      "       "     400     "  "  •«.      "  

"      "       "     500     "  •«  M       «•  ... 


66.30 
9.45 
12.60 
15.75 
18.90 


Extras  to  Standard  Steel  Tape  Measures. 


Each  additional  graduation  and  figuring. 
Reel,  handle  and  stop  to  wind  up  tape, 
2  large  brass  handles  to  unship, 
Clamping  handles,  each, 
Small  brass  clamp  to  fasten  on  tape, 


$0.20 

3.50 

2.50 

1.50 

.75 


So.  191 

44  192 
"  193 
e*  194 


Metric  Steel  and  Metallic  Tape  Measures. 

In  Leather  Boxes. 

20  Meter  Steel  Tape,  divided  in  meters  and  centimeters,  9mm.  wide  $11.00 
10     "        ki        "  fck  »•  u  9         "  600 

20     '4    Metallic  Tape,  divided  in  meters  and  centimeters,  17  mm.  wide  3.50 
10     "    Metallic  Tape,  divided  in  meters  and  centimeters,  17  mm.  wide  2.75 


Jtfo.  195.  Surveyors'  Chain,  2  poles,  50  links,  No.  12  best  steel  wire,  brazed 

links  and  rings, $5.50 

"  196.  Surveyors'  Cham,  4  poles,  100 links,  No.  12  best  steel  wire,  brazed 

links  and  rings, 9.00 

"  197.  Engineers'  Chain,  50  feet,  50  links,  No.  12  best  steel  wire,  brazed 

links  and  rings, 6.00 

"  198.  Engineers'  Chain,  100  feet,  100  links,  No.  12  best  steel  wire,  brazed 

links  and  rings, 10.00 

Metric  Chains. 

No.  199.  20  Meter  Chain,  100  links,No.  12  best  steel  wire,  brazed  links  and  rings,  10.00 
"    200.  10       "        "        50     ^  "  "  "        "  "          5.50 

Extras  to  Tapes  and  Chains. 

No.  201.  Pocket  Thermometer, $1.50 

"    202.  Spring  Balance  and  Level, 5.00 


No.  203.  Set  of  Marking  Pins,  eleven  in  a  set,  steel  wire,  No.  6,  .        .        $1.50 

Odometer. 

No.  204.  An  instrument  for  measuring  distances  traveled  by  carriage,       .        $15.00 

Pedometer. 

No.  205.  An  instrument  for  measuring  distances  walked,  in  german  silver 

case,  of  the  size  of  a  watch, $5.00 


244 

C.  L.  BKRGEK  &  SONS. 


Lamp  for  Illuminating:  Cross  Wires* 


No.  209.  Lamp  for  illuminating  cross  wires  through  the  axis  of  the 
telescope  when  mounted  at  the  side,  for  use  in  underground 
work,  of  brass  and  nickel-plated,  with  ground  lens,  .  $7.00 

•*  210.  Small  Plummet  Lamp,  Of  brass,  steel  point,  16  oz.,     .         8.00 
44  211.  Large  Plummet  Lamp,  of  brass,  steel  point,  24  oz.,         .    10.00 
Box  with  shoulder  straps,  for  pair  of  Plummet  Lamps,         8.00 


No.  210. 


Plummet  Lamp. 


tfo.  212. 


No.  214.       No. 


Plumb  Bobs  of  Precision. 


No.  212.  Plumb  Bob  of  Brass,  steel  point,  shape  as  in  cut,  8  oz., $1.75 

213.  "               "                "             "       "  No.  212,  11  oz., 200 

214.  "               "                "             "        "incut,  6  oz.,        .                 .        .  1.75 

215.  "               "               "             "        "  No.  214,  9  oz.,                    a  200 

216.  "               "                "           patent  reel  adjustment,  8  oz.,                            .        .        .  1.75 

217.  "               "                "               "        "            "           12  oz., 2.25 

218.  "               "        with  steel  shank  passing  through  the  body  for  shaft  work,  3  lb.,      .  &00 

219.  "               "               "                                                  "                "                "        41b.,      .  7.50 

220.  Mercury  Plumb  Bob  (body  of  steel)  12  oz.,  5%  inches  long  %  inch  diameter               .        .  2.25 

«    '             "                    "             I6oz.,6              "            1     "           "  2.75 


245 


Pocket  Magnifiers. 


No.  221 


No.  224. 


No.  221.  Zylonite  Case,  as  in  cut,  size  of  lens  1  inch  diameter,      .        .        .  |o.60 

"    222.        "           "          "     221,     k'       "        IX ...  .90 

"    223.        "          "          l'      221,     "       "        iy2    •>                        ...  1.15 

"    224.       "          "         u     cut      u  of  lenses,  \%  and  1%  in  diameter,         .  1.30 


Gossamer,  Craveiiette  and  Silk  Bags. 

No.  225.  Gossamer  or  Waterproof  Bag,  to  cover  Level  in  case  of  rain  or  dust, 
"   226.  Silk  Bag,  to  cover  Transit  with  solid  silver  graduations 
'*  226a.  Cravenette  Bag  to  cover  Transit,        ..... 


Lubricants. 

No.  227.  Bottle  of  Fine  Watch  Oil,  for  lubricating  Transit  Centers,  etc.  . 


Utensils  for  Cleaning  Instruments. 

No.  228.  Camel's  Hair  Brush 

"   229.  Stiff  Brush  for  cleaning  screw-threads 

u   230.  Chamois-skin  for  cleaning  lenses,  centers,  etc.    . 

"   231.  Stick  for  cleaning  centers 


$1.00 
1.00 
1.00 


.$0.40 
.40 
.50 
.30 


Spirit  Levels. 

No.  232.  Engineers'  Spirit  Levels  of  all  sizes  and  grades  of  «ensitiveness,  accu- 
rately ground  and  tested  by  us. 
Per  inch,  according  to  length  and  diameter      .... 


from  $0*80  to  $1.00 


Surveyor's  Umbrella 

Large,  well-made  umbrella  designed  as  a  protection 
from  sun's  rays  and  wind,  during  field  work.  Staff  pro- 
vided with  a  side  socket  and  shoe.  Umbrella  has  rings 
to  which  guy  lines  may  be  attached. 


Code  word,   Tycuin 


Price  $6.OO 


246 


Portable  Anemometers. 

These  instruments  are  extensively  used  in 
studying  and  controlling  the  ventilation  of 
dwellings,  public  buildings,  factories,  mines, 
etc. 

The  velocity  of  the  air  current  is  measured 
by  means  of  a  very  light  fan  wheel,  whose 
revolutions  are  recorded  on  a  dial. 

This  fan  wheel  is  very  delicate,  the  vanes 
being  made  of  aluminum,  and  the  axis  of  hard 
steel  runs  in  j^wel  bearings. 

The  counting  mechanism  is  enclosed  in  a 
dust-pro~f  case,  and  can  readily  be  thrown 
into  or  out  of  action  by  a  disconnecting  lever. 

The  instrument  is  provided  with  a  thumb- 
sere  w  for  attaching  it  to  a  rod  for  use  in  meas- 
uring the  velocity  of  air  currents  at  any  point 
on  the  surface  of  the  earth,  mine  shafts,  in 
pipes,  conduits  or  narrow  channels.  In  this 
case  the  c  -anting  mechanism  is  thrown  in  or 
out  of  gear  by  pulling  on  cords  of  different 
colors. 

This  A  nemometer  is  carefully  rated  and  sup- 

plied  WITH  A  CORRECTION  NUMBER. 

Anemometer,  Counting  up  to  10,000, OOP 
ft. ;  diameter  of  fan,  Gin. ;  complete,  packed  in 
polished  wooden  box,  $3O.OO. 


The  Brunton  Patent  Pocket  Mine  Transit. 

A  pocket  instrument  which  takes  the  place  of  a  sighting  compass,  clinometer,  pris- 
matic compass,  and  an  Abney  level  or  Locke's  level.  Weight  8  ounces.  Price,  $2O.OO 

Brunton  Mine  Transit  with  leather  sling  case,         .         .         .  22.25 


247 

NEW  PARTS  FOR  OUR  TRANSITS  ANI>  LEVELS  LIABLE  TO  LOSS 

OR  ACCIDENT. 

The  following  list  of  parts  of  our  Transits  and  Levels  can  be  supplied  in  emergency  cases 
when  it  is  impossible  to  send  us  the  instrument.  (Articles  not  given  in  this  list  cannot  be  fur- 
nished unless  the  instrument  is  sent. ) 

NOTE-  As  we  make  many  styles  and  sizes  of  instruments,  a  mere  description  in  your  letter  of 
what  is  wanted  may  not  be  sufficient.  For  this  reason  to  prevent  mistakes  and  loss  of  time  we 
always  require  the  serial  number  and  size  of  the  instrument,  and  a  rough  sketch 
when  the  list  below  and  the  names  given  in  the  cross-section  cut  on  pages  29  and  GO  do  not 
indicate  the  parts  wanted.  Sending  the  broken  pieces  will  also  help  to  identify  the  part  and  the 
size. 

We  cannot  undertake  to  work  by  sketch  or  measures,  and  only  agree  to  send  the  parts  men- 
tioned in  this  list  to  fit  as  near  as  possible  without  having  the  instrument.  (If  we  are  to  do  the 
fitting  to  detached  parts  sent  to  us  there  will  be  an  extra  charge  made  for  such  final  fitting  in 
addition  to  the  price  given  in  the  list  below.) 

Parts  marked  thus(*)  can  be  sent  to  fit  approximately  only.  In  all  cases  where  single 
parts  sent  out  such  as  a  leveling  or  a  tangent  screw  fits  too  tightly  or  too  loosely  a  competent 
instrument  maker  should  make  the  final  fitting,  and  it  is  only  when  too  far  removed  from  one 
that  a  good  local  optician,  jeweller  or  watch  maker  should  do  it. — If  there  is  no  one  to  make  the 
final  fitting  in  the  town  or  vicinity,  send  us  with  the  order  the  parts,  such  as  the  bracket  for 
which  the  new  tangent  screw  is  required,  or  the  leveling  head  for  leveling  screws,  or  level  mount- 
ing tubes,  frames  for  glass  shades,  etc.,  for  proper  fitting. 

Under  no  circumstances  ever  detach  a  standard,  center,  horizontal  circle,  verniers,  or  level  arms, 
etc.,  from  the  instrument. 

Before  ordering  an  article  from  the  list  below,  please  read  Notes  A.  B.  C.  etc., 
page  249. 

When  applying  any  personal  treatment  to  parts  requiring  care,  it  will  be  well  to  first  read  the 
various  chapters  on  '•  Care  of  our  instruments,"  etc.,  on  pages  10  to  22  of  our  Manual, 
which  is  sent  out  with  each  instrument  purchased  also  the  various  notes  appended  to  this  list. 

Emery  must  never  be  used  in  any  form  under  any  circumstances  for  fitting  as  this 
would  spoil  the  part  treated. 

Parts  sent  to  us  by  mail  should  be  REGISTERED  to  ensure  delivery. 

The  prices  below  do  not  include  registration.  Add  1C  cents  if  registra- 
tion is  desired. 

In  order  to  avoid  opening  accounts  for  small  amounts,  the  price,  including  postage,  (and 
registration  if  any  )  should  accompany  the  order. 


NEW  PARTS  FOR  TRANSITS 

SL/B/FPT    Tn  For  illustration  see  page    29. 

WITHOUT  IVOT/CE 

Hood:  (Cravenette  is  supplied  for  Transits,  unless  silk  is  specified)  . 


Price  Postage  Code 
$1.00      .04         Acerb 


(New  box  cannot  be  supplied  without  having  the  instrument.) 

Plumb  bobs,  see  page  244.     For  Transits  No.  1  and  5  use  No.  213  2.00  .12  Ache 

„   2,3,4,6  „     „      212.           .  1.75  .09  Achor 

Plumb  bob  adjuster.           .........  .15  .01  Acute 

Pocket  magnifying    glasses,  see  page  245.     For  all  styles  and  sizes  of 

Transit  except                                       No.  4  use  No.  222           ...  .90  .02  Adore 

For  No.  4  use  No.  221   .           .           .  .60  .02  Aigre 

Set  of  rubber  cushion*  (4)  for  outside  bottom  of  mahogany  box  .30  .02  Alcor 

Adjusting  pins             ..........  .08  .01  Alpia 

Instrument   packing    piece    (brass  ring   to  screw  instrument   upon  the  slide 

board)  1.00  .10  Amber 


Tripod: 


(For  entire  tripods  see  page  158O.) 

Tripod  head  (See  Note  B  )  for  instruments  having  four  leveling  screws 
'  "     complete  with  bolts,  nuts  and  washers 

bolt @$.90)    . 

nut  .          .          .          .          .          .    @  .35  [  see  Note  C 

washer  1.     2.      3.  .  .  .    ©   .05) 

cap  of  aluminum         .... 

leg  full  length,  split, 
"     extension  (See  Note  D) 

shoe  1.     2.     3. 

V     clamp  for  extension  leg  (See  Note  C ) 


1.50 
3.00 
4.25 
.35 
1.00 


.35 
.50 
.04 
.02 
.01 
.10 
Ex 
Ex 
.06 
.07 


Babel 

Dacca 

Badge 

Bafta* 

Balmy 

Banco 

Bandy 

Basis 

Baton 

Bavin 


PRICES  SUBJECT  TO  CHANGE 
WITHOUT  NOTICE 

Leveling:  Head: 


248 


'Leveling  screw  with  ball  and  socket  cup  attached  (See  Note  A) 

Cup  only  for  leveling  screw   ......... 
Foot-plate  on  which  instrument  is  mounted. 
Spiral  Spring  for  tangent  motion          ..... 
Spring  bolt  or  plunger 

@  1.80 
@     .25 
4.50 
.20 
25 

.04 
.01 
.30 
.01 
.01 

Capal 
Caddy 
Cairn 
Calid 
Canal 

Screw  cap  at  end  of  spring  box  case       ...... 
Hook  and  chain  for  plumb  bob  suspension* 

!25 
.10 

'.01 

Caper 
Calmy 

Horizontal  Circle  and  Vernier  Plate: 

Clamp  screw      ......... 

1.20 

.02 

Dace 

*Tangent  screw  (see  Note  A  )...... 

1.00 

.02 

Dais 

*  Vernier  glass,  of  piano-parallel  crystal  glass.  (See  Note  E)      . 
Ground  glass  shade  for  vernier    .           .           .               "       "        . 

1.00 
.60 

.03 
031 

Dater 
Delve 

Shade  frame  for  ground  glass  shade   (See  Note  E) 

1.20 

.02 

Divan 

Spiral  spring      ......... 
Spring  bolt  or  plunger  .               ...... 

Screw  cap  to  hold  spring  in  case    ...... 

.20 
.25 
.25 

.01 
.01 
.01 

Depth 
Digit 
Ditch 

Compass: 

Needle,   (See  Note  F)  and  pivot  (must  be  fitted  to  the  instrument) 

5.00 

Domal 

Pivot             

.50 

Donzcl 

Glass  cover,   (piano-parallel  crystal  glass)      ...... 

1.00 

.14 

Kldain 

Telescope's-  Cross  Axis: 

Clamp  screw  (See  Note  G  )  .          

1.00 

.03 

Fadge 

.20 

.01 

Fagot 

Spring  bolt                                                     ....••• 

.25 

01 

•*-  •"•f**** 
Fancy 

Screw  cap  for  spring  case     ......... 

.25 

.01 

Feint 

Acorns   (protecting  ends  of  cross  axis  )    . 

@   .50 

.02 

Felon 

Vertical  Circle: 

Screws  for  guard. 


.25      .01        Gnarl 


Telescope: 


(We  cannot  supply  new  object  glasses  and  eye-pieces  without 
having  the  instrument,  or  at  least  the  telescope.     See  Note  H. ) 
Cross  and  stadia  -wires  (see  Note  I. ) 
Cap  for  object  glass  for  sizes  No.  1  and  2  Transit,  (11"  to  H"  dia.) 

No.  4  Transit       .        (1J*  and  less  dia)    . 
"  eye-piece  erecting  ....... 

inverting          ....... 

Sunshade,  for  transits  of  our  regular  size  and  kinds  give  diameter 
where  it  is  to  fit 


1.00 

.80 

1.20 

1.00 


.02 
.02 
.02 
.02 


Haifv 
liaise 
Harsh 
Helix 


.75  and  1.00      .04        Hoist 


Spirit  Levels: 


Plate  level,  finely  ground  and  graduated        ......  $1.50  .05       Ibex 

Mounted  in  its  tube  when  latter  is  sent  us  including  registration        .  1.95                 Ichor 

Standard  level  finely  ground  and  graduated           .....  1.50  .05       Ideal 

Mounted  in  its  tube  when  latter  is  sent  us  including  registration        .  1.95                  Ides 

Telescope  level  finely  ground  and  graduated          .....  3.50  .05       Image 

Mounted  in  its  tube  when  latter  is  sent  us  including  registration        .  4.00                 Imban 

Adjusting  nut    ...........  .20  .01        Incog 


NEW  PARTS  FOR  WYE  AND  DUMPY  LEVELS 

For  illustration  see  page  6O. 


For  prices  of  other  parts  not  given  here  see  above  list  of  New  Parts  for  Transits. 


Hood  of  gossamer  rubber,  give  length  of  telescope  over  all 
Stirrup  locking  pin    .        . 

Center  nut  at  bottom  of  spindle   ..... 
Spirit  level,  finely  ground  and  graduated,      $4.50 

Mounted  in  its  tube  when  latter  is  sent  us.    5.00 


1.00 
.70 
.35 


.05 
.01 
.01 
.25f 


Jadea 
Jamb 
Javel 
Jetty 


249 

NOTES  TO  THE  PRECEDING  LIST  OF  ARTICLES 
SUPPLIED  BY  MAIL. 

A.  Concerning  Tangent  and  Leveling-  Screws. 

Tangent  and  leveling  screws  can  only  be  made  to  fit  as  nearly  as  possible  without  having  the  instrument  in  our 
shop.  Both  kinds  are  micrometer  screws,  made  with  great  care  and  fitted  to  the  particular  instrument,  and,  therefore, 
are  not  interchangeable.  When  possible  the  tangent  piece  or  bracket,  or  in  the  case  of  a  leveling  screw  the  whole 
leveling  head  should  be  sent  us,  so  that  we  can  fit  it  properly. 

If  for  instance  the  tangent  screw  sent  you  in  the  absence  of  the  tangent  piece  or  bracket  should  fit  too 
tightly  and  you  have  nobody  to  fit  it,  then  if  you  can  wait,  unscrew  the  tangent  piece  and  send  it  to  us  by  regis- 
tered mail.  Make  sure  to  replace  each  small  screw  into  its  screw  hole  in  the  plate.  If  the  screws  are  transposed 
they  may  project  through,  touching  the  circle  and  injuring  it. 

If  you  have  an  instrument  repairer  in  your  vicinity,  he  can  fit  the  screw  by  working  it  in  and  out  in  its  nut 
with  a  little  tallow  until  it  works  freely,  then  in  the  temperate  or  frigid  zone  the  tallow  must  be  removed  from  the 
screw  and  female  thread  by  using  a  little  benzine  on  a  rag  wrapped  around  a  stick.  When  free  from  -tallow  a  little 
watch  oil  or  vaseline  should  be  applied  as  a  lubricant.  A  jeweler  or  optician  should  be  able  to  do  this. 

Under  no  circumstances  should,  aay  emery  be  used  on  one  of  these  screws,  as  this  would  spoil  it  for 
ever.  If  nat  successful  the  entire  tangent  piece  and  the  screw  should  be  sent  us  by  registered  mail,  as  already 
mentioned. 

«A-:VOTKIK.  Tripod  head. 

When  a  new  tripod  head  is  required  for  an  instrument  having  four  leveling  screws  on  account  of  its  being 
bent,  or  the  screw  threads  worn  too  loose,  then  generally  a  new  lower  foot-plate  to  leveling  head  (see  list  above) 
and  a  new  packing  piece  to  screw  instrument  to  the  slide  board  in  box  will  be  needed  also. 

I 

49-NOTEC.          Tripod  bolts,  nuts,  washers,  clamps  and  shoes. 

Send  us  an  outline  sketch  on  paper  obtained  by  running  a  sharp  pointed  pencil  closely  around  the  article 
desired. 

«3-NOTJ2  ».  Tripod  legs. 

As  the  extension  tripod  legs  and  clamps  vary  in  size  and  have  been  changed  in  style  from  those  formerly  sup- 
plied, it  will  be  necessary  to  denote  the  size  by  sending  the  outline  obtained  as  in  Note  C. 

*£-;VOTKK.          Glass  shades,  vernier  glasses  and  shade  frame. 

Send  the  broken  pieces  or  an  outline  sketch  as  described  in  Note  C.  If  the  vernier  glasses,  etc.,  sent  are  too  large 
a  local  optician  may  grind  them  to  size.  If  too  loose  the  frame  should  be  narrowed  at  the  top. 

49-NOTEF.  Magnetic  needle. 

When  a  new  needle  seems  to  be  required  on  account  of  loss  of  magnetism,  the  trouble  is  usually  that  the  point 
of  the  pivot  is  dull  and  then  needs  to  be  carefully  sharpened  to  a  fine  point  or  that  the  Jewel 
cap  may  have  It -come  rougn  or  rusty  and  needs  to  be  polished — .%.  very  little  magnetism  is 
required  to  make  the  needle  work  satisfactorily  when  the  pivot  point  is  sharp  and  the  cap  well  polished. 
— To  preserve  the  sharpness  of  the  pivot  It  Is  necessary  to  use  great  care  In  lowering  the 
needle  onto  the  center  point,  since  it  may  be  dulled  the  first  time  it  is  used  if  the  needle  is 
dropped  carelessly  upon  its  pivot. 

49-rvoTE  G.  Clamp  screws  to  the  telescope's  axis. 

Only  an  ordinary  regular  telescope  clamp  screw  can  be  supplied.  All  transits  provided  with  a  striding  level 
or  a  solar  attachment  require  a  clamp  screw  especially  made  with  head  of  smaller  diameter  to  enable  the  passage 
of  these  features  around  the  head  of  the  clamp  screw  when  the  telescope  is  revolved  on  its  horizontal  axis.  A 
sketch  with  the  size  and  length  of  head  is  to  accompany  the  order. 

49-NOTEH.  Object  glass  and  Eye-piece. 

Sometimes  it  happens  that  an  object  glass  is  slightly  warped  by  the  excessive  heat  of  summer,  shown  by  a 
distortion  of  the  image,  making  it  impossible  to  obtain  a  sharp,  well  Defined  image,  or  that  the  extreme  cold  of 
winter  may  crack  the  balsam  (see  description  of  the  telescope  page  31 N  with  which  the  lenses  are  cemented  to- 
gether, shown  by  numerous  streaks  or  stars.  (A  few  such  streaks  or  stars  are  not  hurtful,  since  they  cut  out 
only  a  very  small  amount  of  light.)  Such  an  object  glass  should  be  sent  to  us  for  recementing.  Then,  in  most 
cases,  a  new  cell  is  also  needed  in  which  to  mount  it  again  which  adds  to  the  cost  of  repairing. 

In  every  permissib'e  case  the  entire  telescope  should  be  sent  us.  After  the  object  glass  or  telescope  is  returned 
to  the  sender  it  it  neeesiary  to  readjust  the  cross  wires  for  coiiimatlon  as  explained  under  "Ad- 
justments" on  page  54  of  catalog. 

49-NOTEi.  Stadia  wires. 

Stadia  wires  must  be  fitted  specially  to  the  focal  length  of  each  object  glass,  and  therefore,  we  should  receive 
the  entire  te.lescope  If  possible,  or  at  least  ihe  object  glaan,  and  it  will  also  b«  well  to  atato 
whether  the  telescope  is  erect  or  inverting,  a*  otherwise  w«  can  only  furnish  the  wires  ap- 
proximately correct. 

When  a  new  object  glass  is  required,  now  stadia  wires  as  a  rule  must  be  supplied  also. 


250 


J  Tripod  Head 

2  //     Bolt 

3  *      .*   Nut 

4  //     //  Waster 

5  *    Leg   * 

€  FootPlate 

7  Bal/andSocketJoint 

8  Lew/ing  Head 

9  „ 
/O      // 

11  Shi  ft  ing  Plate 

12  Plumb  BobSuspending  cup 

13  *     *  Chain  and  Hook 

14  Repeating  Center 

15  Clamp  Collar 

16  Lover  Clamp. 

17  H  *    Thumbscrew 

18  u  »  Tangent6cretf 

19  »  //  Spring,riotShc/w/i 

20  *  //  PistorMfotshonff> 

21  //  *  Cap.  Not  Shown 

22  Inner  center  -79 

23  Horizontal  Circle 

24  Vernier  Plate  C/amp  80 

25  i>       »        •    <Scretf 

26  Vernier  Plate 

27  *       *   Tanaent Brae  feet 

28  » 

29  *       „       *    Spring 

30  Tange/itSpringP/ston 

31  *       „     cap 

32  Horizontal  Vernier 

33  VemierCorer&ass 

34  *   Shade  frame 

35  ,.  Glass 

36  Compass  CorerGtass 

37  tfeedle 

38  *    P/wt 

39  „    Lifter 

40  A      //     Screw  Head 

41  Front  Plate  Lewi 

42  ,       *  V/ff/ 

43  *      n       *  MjustingMfc 

44  //       //       >/   Rocker 


51  Side  Le&l  Rocker 

52  »«    rial 

53  Telescope  fa/s 
$4     i        Barrel 
55  Fye  p/ece  Mounting 


46  »       JJaJustable  M/e  Bearing 

47  »      CapandScretxs 


49  »    »  Adjusting  Screw 

50  *    »  Fastening  jcrev 


57  Terrestr/a/  Eye  Piece 

58  £t/ePieceCap 

,     *  ffing 


63  *   Head 

64  u     u  Sere* 

65  u     H  <Sadd/e 


66  u     u    u  Screws 

67  fbject  Slide 

68  //     Head 

69  n     Glass  cell 

70  H     Glass 


72  JunSnade 

73  Te/escope  Clamp 

74  tt          * 

75  „          „  mster 


77  Yert/caltirc/e 

78  « 

79  u 


80  tertical  termer 
8/     /         *  Screw 


Cross  section  of  the  Berger  Transit. 


1 .  L.  BEKGEK  &  SONS. 


INDEX 


PAGE 

Abney  Level  and  Clinometer 119 

Adjustable  Center  for  Mine  Transits 202 

Plumb-Bob 7,  52,  244 

Adjustments  of  Auxiliary  Side  and  Top  Tel- 
escope        93-97 

"  Axis      of      Revolution      with 

Striding  Level 57 

"  Cross  Wires         22,  54-55,  58,  93-97 

"  Dumpy  Levels 63 

"  Instruments 20-27 

"  Level  to  Telescope  .  55,  59,  62-64 
"  Line  of  Collimation  ....  58 
"  Striding  Level,  Resting  on 

Special  Collars 56 

"  Striding      Level,     Improved, 

Resting  on  Special  Collars        57 
"  Striding    Level,    Resting    at 

Points  of  Contact  in  Wyes       57 
"  Telescope  Standards    ....        54 

"  Transits 53 

"  Vertical  Arc  or  Circle    ...        55 

"  Wye  Levels 62 

Alt-Azimuths 222-224 

Aluminum  for  Instruments  of  Precision     ....       23 

Anemometer,  Portable 246 

Arc,  Beaman  Stadia 155,  197 

"     Movable 196 

"     Pennsylvania 196 

Arc  or  Vertical  Circle,  Adjustment  of 55 

Different  Types     155,  196-200 

Arm  with  Magnifier,  Flexible 202 

Artificial  Horizon 228 

Astronomical  Transits       222-227 

Auxiliary  Telescope,  Style  1,  Interchangeable 

Top  and  Side 93-97,  189-190,  192-195 

Bags,  Gossamer  and  Silk 245 

Beaman  Stadia  Arc 155,  197 

Berger  Solar  Attachment 172 

Adjustment  and  Use 

of 65-92 

Bevel  Limb  Transit 253 

Bracket  for  Underground  Use 203 

Brunton  Pocket  Mine  Transit 246 

Brushes 245 

Care  of  Centers  and  Graduations 11 

"    "  Instruments 10-20 

"    "  Telescope  Lenses 12 

Catalog  and  Price-List      103-253 

Center,  The  Adjustable,  for  Centering  under  a 

given  point      202 

Centers 43 

Care  of 11 

Shifting,  for  Transits 52 

Steel 126,  130,  132,  134,  212 

Centering    Arrangement    for   Transit   over   a 

given  point 52 

Chains,  Engineers'  and  Surveyors' 243 

Chesterman  Tapes 238 

Circles,  Reflecting      228 

Vertical 56,  155,  199-200 

Circles  and  Verniers,  Graduation  of    ...      37-42 

City  Transits 150-169,212-221 

Clinometer 119 

Collimation,  Line  of 22 

Compass,  Surveyors'  Transit      7,  43 

Marine 235 

Miners' 235 

Needle 98-99 

Oblong 212 

Pocket      235.  246 


PAGE 

Compass,  Prismatic 235 

Surveyors' 235 

Vernier  Pocket 235 

Construction  of  Instruments      .    . 8 

Cross-Level,  Revolving 201 

Cross  Section  of  Spirit  Levels 26 

"  Transit 29,  250 

"  Transit  Telescopes 30 

"          "  Wye  Level       60 

"          "  Wye  Level  Telescopes      ...        61 

Cross  Wires 16,  22,  51,  54,  56,  93-96 

Adjustment  of    .    .    22,  54-55,  58,  93-97 

Illumination  of 8,  220 

Replacement  of  Broken 16 

Current  Meters 230-232 

Davis'  Solar  Attachment 174-175 

Adjustment  and  Use        81 

Declination,  Reduction 67-68,  80 

Observation      83-84 

Diaphragms,  Different  Styles  of  Wire     ....      122 

Disappearing  Stadia  Wires 190 

Distance  Measurements  by  Stadia  Wires  .    .     6,  88-92 
Double  Opposite  Vernier  Attachment ....      155 

Dumpy  Levels,  Engineers' 123-129 

Adjustment  of 63 

Dust  Guard,  Collapsible 128 

Edge  Graduation  for  Vertical  Circle     .    .      198-199 

Excelsior  Tapes 239 

Eye  Piece,  Diagonal 175 

Pancratic 34 

Face  Graduation  for  Vertical  Circle     .    .      199-200 

Finish,  Styles  of 9 

Gradienter  Screw 6,  45 

Tables 48-51 

Graduations 5,  34-42 

Care  of 10 

Hand  Levels      119 

Hoods,  Gossamer  and  Silk 245 

Horizon,  Artificial      228 

Hydrographers'  Wye  Level 136-137 

Illumination  of  Cross  Wires 8,  220 

Improved  Prism  and  Colored  Glass  Attach- 
ment         174-175 

Inclined  Square 174 

Instruments,  Adjustment  of     ...  20,  27-67,  93-97 

Care  of 10-22 

"  General  Construction  of    ....         8 

Repairs  to 25 

Transportation  of 18 

Interchangeable    Top     and     Side     Auxiliary 

Telescope,  Style  I 93-97, 189-195 

Lamp  Targets 209 

Lamps,  Mining,  Engineering  and  Plummet   .    .    .     244 

Lateral  Adjuster      205-207 

Latitude  Level  Attachment         .          68,  85,  171-173 
Observation,  Portable  Instruments  for     226 

Leather  Finish 9 

Lenses,  Care  of 12-13 

Short  Focus 100-101,  190,  203 

Level  Triers 117 

Levels,  Abney 119 

Coast  Survey  Precise 144 

Dumpy 123-129 

Adjustment 63-64 

Engineers'  Precise 139-141 

Wye 130-135 

Adjustment 59-62 

Geodetic 142-143 

Hydrographers' 136-137 

Latitude  .  172   173 


C.  !L.  BERGER  &  SONS. 


252 


PAGE 
.      119 
138-155 
,    .      201 
.      237 
.      118 
119 


Levels,  Locke's  Hand 

Reversion 

Revolving  Cross-Level     .    .    . 

Rods •  .    . 

Spirit 

On  Metal  Base  .... 

Stride 201 

Leveling  Attachment,  Quick 8,  45,  118 

Rods 236-237 

Screws 44 

Line  of  Collimation 22 

Locke's  Hand  Level 119 

Lubricants 14,  245 

Lucas'  Steel  Tapes 241 

Lufkin's  Steel  Tapes 239 

Magnifier,  Flexible  Jointed  Arm  with 202 

Magnifier  and  Reflector 198 

Magnifiers 245 

Magnetic  Needles,  Balancing  of 7 

Variation  of 7,  43,  44 

Magnetometer 229 

Magnifying  Glasses 245 

Marine  Compass 235 

Marking  Pins 243 

Measurements  by  Fixed  Stadia  Wires     .    .      88-92 

Meridian,  From  Equal  Altitudes 68 

From  Polaris 78 

Inclination 70 

Tables 77 

Observation  for 71 

Meters,  Current 230-232 

Metric  Chains 243 

Steel  and  Metallic  Tapes 242 

Miners'  Compass 235 

"         Lamps 244 

Mining  Transits      182-209 

Mirror  with  Universal  Joint  .    .    .     127,  137,  140-141 

Mountain  Transits 176-183 

Movable  Arc 196 

Object  Glasses,  Abnormally  Large 33 

Object-Slide,  Protection  to 8 

Oblong  Compass 147,  160,  212 

Odometer 243 

Offsetting  Arrangement 8,  53 

Optical  Adjustment  of  Instruments 27 

"       Principles  of  Engineers'  Telescope    ...       27 

Packing  of  Instruments 9,  18 

Paine's  Tapes 238 

Pancratic  Eye  Piece 34 

Pantograph,  Precision 233 

Parts  of  Instruments 104,  247-249 

Pedometer 243 

Pendulum  Apparatus 229 

Pennsylvania  Arc 196 

Pins,  Marking 243 

Plain  Transits      151,  168 

Plane  Table 146-147 

Planimeters,  Compensation 233 

Rolling  Ball 234 

Suspended  Ball 234 

Plumb-Bobs 7,  244 

Plumbing  and  Centering  Arrangement 52 

14         Device  for  Carrying  a  Line  Down  a 

Shaft      188,  191 

Plummet  Lamp      244 

Pocket  Compass 235 

Magnifiers 245 

Sextant 229 

Tapes 238,  242 

Polaris,  To  Find  Meridian  from 78 

Poles,  Ranging 237 

Portable  Anemometer 246 

Astronomical  Instruments.    .    .      225-227 

Time  Transit 225-227 

Precise  Level,  Coast  Survey 144 

Engineers' 139-141 

Price  List 103 

Prism  and  Colored  Glass  Attachment     .      174-175 

Prismatic  Compass 235 

Protection  of  Instruments    .  14 


PAGE 

Protection  of  Object  Slide 8 

Quick  Leveling  Attachment 8,  45,  118 

Railroad  Transits 150-169 

Ranging  Poles      237 

Reading  Glass  and  Reflector 198 

"    with  Flexible  Arm 202 

Glasses       245 

Reconnoissance  Transits 182-183 

Reflecting  Circle 228 

Repair  of  Instruments 25 

Repairer,  Tape 241 

Replacing  Wires' 16 

Reversion  Levels 138,  155 

Road  Builders'  Dumpy  Level 123 

Rods,  Leveling 236-237 

Roe's  Tapes 241 

Rolling  Ball  Planlmeter 234 

Setting  up  Transits 53 

Sextants 229 

Shifting  Center  for  Transits  with  Three  Level- 
ing Screws 52 

Shifting  Tripod 7 

Short  Focus  Lens 100-101,  190,  203 

Side  Telescope,  Style  1  Interchangeable  Top 

and  Side 93-97,  189-195 

Sizes,   Weights    and    Particulars   of   Instru- 
ments       115 

Solar  Attachments 65-87.  170-174 

Adjustment  and  Use  of  .     65-87 
Coefficients   of    Refraction 

Table 76 

Davis'    ....     81-87,  174-175 
Degree    of    Precision    Re- 
quired for      70 

Direction  and  Use  of  Davis' 

81-87 
"  Form  of  Dally  Declination 

Table 67 

"  General  Remarks  Concern- 

Ing  Use  of  ....  69,  81,  87 
Hourly  Motion  of  Sun's 

Declination 80 

Inclination  of  Meridian  .    .        70 
Inclination    and    Converg- 

ency  of  Meridian,  Table  77 
Mean  Refraction  Tables  73-75 
Reducing  Observation  .  84-87 
Reduction  of  Declination 

and  Refraction  ....  67 
To  Correct  Watch  ....  86 
To  Find  the  Latitude  by  the 

Sun 68,  85 

To  Find  Meridian    ....       68 
To    Find    Meridian    from 

Polaris 78 

To    Find    Meridian    from 

Equal  Altitude  ....  79 
Use  of  Nautical  Almanac  .  83 

Solar  Telescopes      97 

Spider  Lines  of  Various  Diaphragms    .    16,  51,  122 

Spirit  Levels 6,  26,  44,  118,  245 

Care  of 15 

"  "       Mounting 15 

"       On  Metal  Base    .    .  .    .      119 

Spring  Balance  and  Level 243 

Square,  Inclined 174 

Stadia  Arc,  Beaman 155,  197 

Lines 6,  51 

"    Disappearing 190 

Measurements 6,  88-92 

Wires      6,  51,  88,  92 

Standard  Steel  Tapes 242 

Steel  Tapes 238-242 

"      Centers,  Instruments    .    126,  130,  132,  134,  212 

Stride  Levels 

142,  147,  156-159,  185,  201,  209,  213-222 
Striding  Level,  Use  and  Adjustment      ....     56-57 

Suspended  Ball  Planimeter 234 

Suspended  Pantograph 233 

Tachymeters     ...  156-159 


C.  L,.  BERGER  &  SONS. 


253 


PAGE 

Tangent  Screws 7 

Tape  Repairer      241 

Tapes,  Steel  and  Metallic  in  Feet  and  Metric .  238-242 

Chesterman 238 

Lucas 241 

Lufkin 239 

Paine 238 

Roe 241 

Standard  Steel      242 

Telescopes,  Auxiliary  Top   and    Side,    Inter- 
changeable, Style  1       95-97,  189-195 

Description  of 5,  27-31 

Erecting  and  Inverting      32 

Side,  Adjustments  of 93 

Solar , 97 

Spider-line  Diaphragms     ...       51,  122 

Top,  Adjustable      95 

Theodolites 212-219 

Time  Observation      86 

"      Transit 225-226 

Transits,  Adjustments  of 27,  53-59,  93-97 

Astronomical 222-227 

City 150-169 

Cross  Section  of 29-30,  250 

Directions  and  Use  of 53 

Engineers'  and  Surveyors'     .    .      150-169 

General  Construction  of 28 

Mining 182-209,  246 

Mountain 176-183 

Plain 151,  168 

Pocket,  Bmnton  Mine 246 

Railroad       150-169 

Reconnoissance 182-183 


PAGE 

Transits,  Setting  Up 53 

Small,  No.  2,  No.  4J^,  No.  4  .    .      168-186 
Solar  Attachments  for   .     65-80,  172-175 

Surveyors' 150-169 

Theodolite       184-185,  210-220 

Time 225-226 

Triangulation 212-220 

Tunnel 210-216 

Wet  Mine 194-195 

With  Level  Attachment  to  Telescope    152 

Transportation  of  Instruments 18 

Transverse  Striding  Level 57 

Tripods 7,  120-121 

Tripods,  Extension,  See  Note 120,  176 

Half  Length 120,  188 

Split  Leg 120,  188 

Tunnel      207 

Trivets 204 

Tunnel  Transits       210-216 

Tripod 207 

Umbrellas,  Surveyors' 245 

Variation  Plate 7,  43-44,  98-99 

Vernier  Attachment,  Double  Opposite    .      155,  214 

Verniers      37-41 

Vertical  Circles,  Adjustments      55 

Beaman  Stadia  Arc  for  .  .  155,  197 
Edge  Graduation  ....  198-199 
Face  Graduation  ....  199-200 

Watch,  Correcting  by  Sun 86 

Weights  and  Sizes  of  Instruments 115 

Wye  Levels 59-62,  130-137 

Adjustment  of 62 

Engineers'  Hydrographers     .    .          136 


C.  Li.  Berger  &  Sons'  Bevel-Limb  Transit. 

The  above  cut  represents  our  Bevel  Transit  as  made  by  us  to  order  since  1871. 

NOTE.  While  a  bevel-limb  graduation  of  a  horizontal  circle  can  be  somewhat  more  readily  seen  than  one  on  a  horizontal 
surface,  it  is  well  to  remember,  before  ordering  instruments  to  be  made  so,  that  there  are  very  serious  objections  to  their 
general  adoption  for  engineers'  field-instruments.  As  will  be  seen  in  the  annexed  cuts,  the  sharper  and  therefore  more 
delicate  edges  of  the  soft  solid  silver,  necessitated  by  the  bevel  at  the  junction  of  limb  and  verniers,  are  much  more  liable 
to  injury  and  wear  in  field  use  than  the  common  horizontal  graduation,  where  the  same  edges  are  carried  down  nearly  rect- 
angularly below  the  graduated  surface.  Thus,  while  a  bevel  possesses  some  advantages  when  ne-u  and  well  constructed, 
it  soon  becomes  impaired  by  slight  dents  and  the  edges  rounded  by  brush  or  finger  when  dust  and  oxyd  must  be  removed 
at  certain  times.  It  then  can  be  read  only  with  difficulty  and  becomes  a  source  of  great  annoyance,  particularly  as  the  eye 
looks  squarely  at  it,  thus  defeating  the  very  object  sought  and  rendering  the  instrument  almost  unfit  for  good  work,  although 
otherwise  in  good  condition.  We  say  this  with  an  experience  of  twenty-five  years  to  back  up.  To  make  it  plain  we  must 
have  recourse  to  the  diagrams.  Fig.  c  is  the  cross-section  of  a  horizontal  limb  and  vernier  as  commonly  made.  It  is  obvious 
that  the  fine  silver  edges  at  the  junction  of  limb  and  verniers  are  in  this  form  better  protected  from  wear,  and  also  that, 
when  slightly  rounded  by  wear,  or  when  the  graduated  surfaces  are  not  in  the  same  plane,  the  eye,  being  stationed  at  an 
angle  of  about  45°  to  the  limb,  requiring  an  observer  to  glance  along  the  graduated  lines,  will  more  readily  see  and  esti- 
mate differences  in  the  reading  of  limb  and  verniers,  thereby  enabling  him  to  obtain  closer  results,  as  verified  by 
the  superior  results  in  triangulation  obtained  with  horizontal  graduations  over  bevel  ones  formerly  in  vogue.  Fig.  a  is  a 
cross-section  of  a  bevel  limb,  showing  the  sharper  edges  of  the  graduated  surfaces.  When  new  and  properly  made  the  edges 
of  limb  and  verniers  appear  the  same  as  those  in  Fig.  c  and  a  c,  but  when  worn  off  they  will  leave  a  big  circular  space  between 
them,  making  the  reading  of  an  angle  all  the  more  difficult  and  uncertain.  There  are  other  reasons,  against  their  general  adop- 
tion, such  as  that  the  standards  for  the  telescope  have  in  bevel  instruments  not  the  stability  so  important  in  angle-measuring 
instruments  unless  they  are  mounted  on  a  special  horizontal  base  provided  for  them,  (instead  of  on  the  bevel  surface  of  the 
upper  plate)  which  means  a  great  increase  in  weight,  or  that  the  distance  between  them  be  quite  short,  resulting  in  a  shortening 
of  transverse  axis  of  the  telescope,  as  in  the  cut  above,  thereby  increasing  the  instability  of  the  same,  particularly  if  the  tele- 
scope is  of  modern  power  and  length,  besides  reducing  the  size  of  compass,  length  of  plate  levels,  and  with  this  the  degree 
of  sensitiveness  of  the  latter.  In  both  these  instances  the  standards  are  apt  to  change  their  distance  apart  affecting 
the  adjustment  of  the  line  of  collimation  for  near  distances.  —  The  greater  expense  of  repairing,  in  case  of  accident,  is  also 
an  item  that  should  be  considered.  It  is  often  double  or  triple  that  of  a  horizontal  graduation.  To  our  mind  bevel  gradu- 
ation should  be  confined  to  exceptional  cases  and  to  the  larger  instruments  read  by  micrometer  microscopes. 


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